- Email: [email protected]
Manganese induced ZrSiO4 crystallization from ZrO2SiO2 binary oxide system
Ceramics International 45 (2019) 11539–11548
Contents lists available at ScienceDirect
Ceramics International journal homepage: www.elsevier.com/locate/ceramint
Manganese induced ZrSiO4 crystallization from ZrO2eSiO2 binary oxide system
T
S. Vasanthavela, M. Ezhilana, V. Ponnilavana, J.M.F. Ferreirab, S. Kannana,∗ a b
Centre for Nanoscience and Technology, Pondicherry University, Puducherry, 605 014, India Department of Materials and Ceramics Engineering, University of Aveiro, CICECO, Aveiro, 3810 193, Portugal
A R T I C LE I N FO
A B S T R A C T
Keywords: Manganese Zircon Zirconia Silica Structure
The ability of manganese to induce early zircon (ZrSiO4) crystallization is investigated. An assorted range of manganese additions to the ZrO2eSiO2 binary system through a Sol-Gel approach is attempted to achieve ZrSiO4 formation at low temperatures. XRD analysis alongside complementary Rietveld refinement tool has been used to determine the propelling effect of manganese on the low temperature formation of ZrSiO4. The results revealed the ability of 5 wt% manganese to induce the ZrSiO4 formation at 900 °C through its occupancy at the ZrO2 lattice. The lattice substitution of Zr4+ by the lower sized Mn2+ and the concomitant lattice distortion of ZrO2 have been determined as the prime reason for manganese to enhance the reaction kinetics with amorphous SiO2 to yield ZrSiO4. Increments in the manganese content beyond 5 wt% are rejected by the ZrO2 lattice, making the excess to crystallize as Mn2O3. The colour change of ZrSiO4 is directly influenced by the manganese content in ZrO2eSiO2 binary system.
1. Introduction The salient features of low thermal conductivity, thermal shock resistance, high chemical stability and mechanical strength favour zircon (ZrSiO4) use in refractory industries [1–3]. ZrSiO4 derived from natural resources encompasses several impurities, which coupled with inadequate densification ability that restrict the potential technological applications. The synthetic ZrSiO4 derived from the combination of ZrO2 and SiO2 metal oxides is generally accomplished only at elevated heat treatments (> 1500 °C) that led to high manufacturing costs. Therefore, the low temperature synthesis of ZrSiO4 is a topic of interest for refractory industries. In this context, most of the studies envisage the aid of alkaline metal halides and alkaline metal nitrates as mineralizers to induce ZrSiO4 formation in the range of 1000–1200 °C [4–6]. Simultaneously, ZrSiO4 based pigments with tuneable colours have been widely developed by aiding different dopants as chromophores. Vanadium doped blue ZrSiO4, praseodymium doped yellow ZrSiO4 and iron doped pink ZrSiO4 are among the few that are commercially successful in pigment industries [7–12]. In this pursuit, many investigations were devoted to develop ZrSiO4 pigments at low temperature by the use of both dopants and mineralizers. Eppler et al. [13] emphasized the role of mineralizers to yield low temperature ZrSiO4 through the reaction between SiO2 and halides (H). The reaction between Si and halides yields SiH4 species and their migration over ZrO2 ∗
surface has been stated as reason to favour ZrSiO4 formation ∼1000 °C. Nonetheless, ZrSiO4 pigments have been developed at low temperatures only with the aid of dopants that act as chromophores. The literature evinces contradictory reports on the crucial role of dopants and their concentrations to promote of ZrSiO4 formation at low temperatures. In addition, the influence of chemical state of the dopants either in ionic or oxide forms to tune the resultant colour intensity is also poorly understood. In case of iron doped ZrSiO4, Tartaj et al. [14] emphasized the generation of oxygen vacancies in t-ZrO2 lattice by the occupancy of Fe3+ to favour ZrSiO4 nucleation, while the excess Fe3+ beyond the occupancy limit forms hematite (α-Fe2O3) and hence gets segregated throughout the ZrSiO4 matrix. The authors reported that Fe3+ additions till 5 wt% favour the ZrSiO4 formation by the reaction between Fe3+ substituted t-ZrO2 and amorphous SiO2, while the Fe3+ additions beyond 5 wt% crystallize as α-Fe2O3 under oxidative conditions [15]. The studies on praseodymium-doped ZrSiO4 by Badenes et al. [16] and Ocana et al. [17,18] emphasize the occupancy of Pr4+ at triangular dodecahedral sites of Zr4+. On the contrary, Shoyama et al. [19] reported the accommodation of Pr4+ at both triangular dodecahedral sites of Zr4+ and tetrahedral sites of Si4+ to favour ZrSiO4 formation. In a similar manner, the occupancy of vanadium (V4+) in vanadium doped ZrSiO4 systems is also contradictory with either dodecahedral sites of Zr4+ or distorted tetrahedral sites of Si4+ and the both sites [10,20,21].
Corresponding author. E-mail address: [email protected] (S. Kannan).
https://doi.org/10.1016/j.ceramint.2019.03.023 Received 10 December 2018; Received in revised form 27 February 2019; Accepted 5 March 2019 Available online 08 March 2019 0272-8842/ © 2019 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Ceramics International 45 (2019) 11539–11548
S. Vasanthavel, et al.
Further, the development of low temperature ZrSiO4 with other dopants such as Li+, Ni2+, Co2+, FeNbO4 and rare earth elements alongside different mineralizers were investigated and the results ensured the attainment of different colour pigments [22–25]. Nevertheless, the quest to attain unique ZrSiO4 phase at low temperature continues as most of the reported systems witnessed the presence of either ZrO2 (t/m-ZrO2) or cristobalite (c-SiO2) and/or other oxides as minor phases. In this context, the present study aims to investigate the inducing role of manganese in the formation of single phase ZrSiO4 at low temperatures from the ZrO2eSiO2 binary system. A detailed structural analysis is performed to gain quantitative information on the structural features of ZrSiO4 due to manganese additions. 2. Materials and methods 2.1. Powder synthesis Analytical grade zirconium oxychloride octahydrate [ZrOCl2.8H2O], tetra ethyl orthosilicate [(C2H5O)4Si, TEOS] and manganese (II) nitrate tetrahydrate [Mn(NO3)2.4H2O] were used as precursors for the sol-gel synthesis of the powders. Pure stoichiometric ZrO2eSiO2 binary system devoid of Mn2+ additions was prepared for comparative purposes. Compositions based on this ZrO2eSiO2 binary oxide system and containing progressive added amounts of manganese from 2.5 to 30 wt% with respect to the constant molar concentration of ZrO2 in the pure stoichiometric system were also prepared through the same sol-gel technique. The precursor molar concentrations along with their respective sample codes are reported in Table 1. In a brief description of the synthesis, individual stock solutions of ZrOCl2 and Mn(NO3)2 prepared in deionized water were mixed together under vigorous stirring conditions. TEOS solution dissolved in appropriate amount of C2H5OH was also separately prepared. Both solutions were mixed together and subsequently 0.1 M of HNO3 as a catalyst was added and the resultant mixture was allowed to stir until the formation of a precursor gel and thereafter dried at 120 °C overnight. The dried gel samples were grounded to fine powders and subjected to characterization studies after heat treatment at different temperatures with a dwell time for 2 h. 2.2. Powder characterization X-ray diffractometer (Rigaku, ULTIMA IV, Japan) was used to analyse the phase behaviour of powders using a CuKα radiation (k = 1.5406 Å) produced at 40 kV and 30 mA to scan the diffraction angles (2θ) between 10° and 70° with a step size of 0.02° 2θ per second. Standard ICDD (International Centre for Diffraction Data) Card Nos. 01083-1376 for ZrSiO4, 98-000-6458 for Mn2O3, 01-079-1765 for t-ZrO2, 01-083-0944 for m-ZrO2 and 00-076-0941 for cristobalite (c-SiO2) were used for the phase analysis of the powder XRD patterns. Raman spectrum of the powders were recorded using backscattering geometry of Confocal Raman microscope (Renishaw, Gloucestershire, UK) with an excitation wavelength of 785 nm by semiconductor diode laser (0.5% of Table 1 Precursors molar concentrations used for the powder synthesis. Sample code
ZrOCl2
(C2H5O)4Si
Mn(NO3)2
% of Mn2+ with respect to Zr4+
PZS 2.5 MZS 5 MZS 10 MZS 15 MZS 20 MZS 30 MZS
0.5 0.5 0.5 0.5 0.5 0.5 0.5
0.5 0.5 0.5 0.5 0.5 0.5 0.5
– 0.0125 0.025 0.05 0.075 0.10 0.15
– 2.5% 5% 10% 15% 20% 30%
* Denotes the lattice parameters of t-ZrO2.
power) and the data acquiring time of 30 s. The morphological features and selected area diffraction (SAED) patterns were recorded using high resolution transmission electron microscopy (HRTEM, TECNAI G2-F30 ST WIN, USA) associated with a silicon drift detector for energy dispersive X-ray spectroscopy (EDX) analysis. X-ray photoelectron spectroscopy (XPS) technique has been used for the analysis of compositional and chemical state of manganese. XPS was obtained using X-ray Photoelectron spectrometer (ULVAC-PHI, Japan). The binding energy calibrations for the shift in charge were calibrated using the C 1s peak of graphitic carbon (BE = 284.8 eV) setting as standard and binding energy background subtraction was carried out prior to the simulation using Gaussian function. Rietveld refinement of the powder XRD patterns were performed through GSAS-EXPGUI software package [26]. The standard crystallographic data were obtained from American mineralogist crystal structure database for the refinement of ZrSiO4, Mn2O3, t-ZrO2, m-ZrO2 and c-SiO2 as reported by Hazen et al., Norrestam et al., Howard et al., Smith et al. and Dera et al. respectively [27–31]. The Fourier charge density maps obtained from GSAS were viewed with VESTA. The reflectance spectra and corresponding L*, a* and b* parameters for the MZS samples were recorded using Premier colorscan instrument (A5000 model, Navi Mumbai, India). L* indicates the colour lightness (100 for white and 0 for black), a* indicates green (−)/red (+) region and b* denotes the blue (−)/yellow (+) region. 3. Results 3.1. Phase analysis The phase analysis of the pristine and assorted range of manganese additions in ZrO2eSiO2 binary system was determined through X-ray diffraction technique. The XRD patterns of the samples heat treated at 900 °C are displayed in Fig. 1a. The pure ZrO2eSiO2 (PZS) composition confirms the crystallization of single t-ZrO2 phase, while the Mn2+doped compositions (MZS) also ensure t-ZrO2 as being the major crystalline phase. The X-ray reflections of ZrO2eSiO2 system with 2.5 wt% of Mn additions enable to infer about the formation of t-ZrO2 as single phase, similarly to what was observed for PZS, while minor reflections typical of ZrSiO4 seem evident in the composition with 5 wt% of Mn, which tend to intensify upon increasing the Mn content to 10 wt%. The upsurge of Mn2O3 reflections is initially noticed in 10 wt% of Mn and thereafter a progressive intensity is noticed with respect to the increment in Mn additions. A concomitant decline in the intensity of X-ray reflections of ZrSiO4 is witnessed for progressive Mn additions. Moreover, an irregular trend in t- → m-ZrO2 phase transition is also noticed for the intermediate compositions (10MZS and 15MZS). The XRD patterns of the investigated compositions exhibit good consistency with their corresponding standard ICDD patterns respective of t-ZrO2, ZrSiO4 and Mn2O3. For the samples heat treated at 1000 °C, the XRD patterns (Fig. 1b) reveal the presence of single t-ZrO2 phase for PZS and 2.5MZS, while reflections of ZrSiO4 as dominant crystalline phase are witnessed in the remaining MZS compositions. The progressive increasing intensity trend of Mn2O3 reflections with incremental Mn2+ concentrations noticed at 900 °C is also replicated at 1000 °C. Moreover, t-ZrO2 and cristobalite (c-SiO2) are also determined as minor phases in the compositions with incremental Mn additions. With further increasing the heat treatment temperature to 1100 °C (Figure S1), the crystallization of ZrSiO4 is already obvious for 2.5MZS, whereas the XRD patterns of other MZS compositions displayed a good cohesion with the trend observed at 1000 °C. The XRD patterns obtained at 1200 °C (Fig. 1c) ensure the manifestation of ZrSiO4 in PZS sample. Despite the ZrSiO4 formation, t-ZrO2 is determined as a dominant component in PZS alongside a minor level of t→m-ZrO2 phase transition at 1200 °C. In terms of MZS, reflections typical of t-ZrO2 and c-SiO2 are observed in minor level for 2.5MZS and thereafter a gradual decline in their reflections is noticed for the incremental Mn2+ concentrations. On the
11540
Ceramics International 45 (2019) 11539–11548
S. Vasanthavel, et al.
Fig. 1. XRD patterns of PZS and Mn2+ doped ZrO2eSiO2 binary system recorded after heat treatment at different temperatures. Fig. 1a-d correspond to the patterns recorded respectively at 900, 1000, 1200 and 1300 °C.
contrary, the reflections distinctive of Mn2O3 demonstrate a gradual upsurge from 10MZS with respect to the incremental Mn2+ concentrations. PZS infers the presence of dominant ZrSiO4 at 1300 °C (Fig. 1d) alongside t-ZrO2, m-ZrO2 and c-SiO2 components complimented by their corresponding minor reflections. On the other hand, 5MZS ensured the formation of ZrSiO4 as a single phase at 1300 °C, while the other MZS compositions replicated the similar trend of 1200 °C. 3.2. Raman spectroscopy The Raman spectra recorded at 900 °C (Fig. 2a) exhibit good coherence with their corresponding XRD patterns. 2.5MZS showed the bands typical of t-ZrO2 while 5MZS, 10MZS and 15MZS confirm the combination of t-ZrO2 and ZrSiO4 bands at 900 °C. The bands observed at 148, 270, 317, 353, 456, 641 cm−1 are attributed to t-ZrO2 [32–34] while the 976 and 1008 cm−1 bands are assigned to symmetric ν1(SiO4) stretching and antisymmetric ν3(SiO4) stretching vibrations of ZrSiO4 [35–37]. Nonetheless, the other bands typical of ZrSiO4 at lower frequencies are negligible in 5MZS due to the dominant nature of t-ZrO2 at 900 °C. The progressive surge in the intensity of distinct ZrSiO4 bands, together with the simultaneous decline in t-ZrO2 bands are inevitable in 10MZS and 15MZS. Moreover, the characteristic ZrSiO4 bands at lower frequencies emerge from 10MZS and are more evident in 15MZS, which are in good agreement with the XRD results. The lower frequency bands at 202, 214, and 225 cm−1 are attributed to the vibrations amongst Zr4+ and SiO4 tetrahedron while 356 and 439 cm−1 bands is signposted for ν2(SiO4) antisymmetric bending and ν2(SiO4) symmetric bending vibrations, respectively. The less intense 393 cm−1 band is hardly
reported as an internal lattice vibration of ZrSiO4. The bands typical of t-ZrO2 and ZrSiO4 are barely visible in 20MZS and 30MZS and further the Raman bands corresponding to Mn2O3 are found negligible in all the MZS systems at 900 °C. The Raman spectra of 2.5MZS at 1000 °C (Fig. 2b) display the presence of typical t-ZrO2 bands while the distinct ZrSiO4 vibrations alongside a discrete 279 cm−1 band respective of t-ZrO2 is determined for 5MZS. The other common bands of t-ZrO2 are barely found in 5MZS while the remaining MZS systems signify the complete absence of tZrO2 bands. This contradicts the results gathered by XRD pointing out to the presence of ZrO2 (t/m-ZrO2) traces. The absence of distinct ZrO2 bands is mainly attributed to the high intensity ZrSiO4 bands. However, the reduced intensity of ZrSiO4 bands is also observed for the incremental Mn2+ additions. Moreover, the absence of typical Mn2O3 bands is evident at both 900 and 1000 °C. Similar to the XRD results, the Raman spectra recorded at 1300 °C (Fig. 2c) enunciate the formation of sole ZrSiO4 vibrations in case of 5MZS. While other MZS compositions also perceived a similar result of dominant ZrSiO4 vibrations; however, the negligence to detect typical Mn2O3 bands in these compositions at 1300 °C is mainly complimented by the dominant ZrSiO4 that intend to suppress vibrations pertinent to Mn2O3 and other minor phases. 3.3. Transmission electron microscopy Transmission electron micrographs of 5MZS heat treated at 900 °C (Fig. 3a and b) depict the distribution of crystalline fringes in an amorphous matrix. A close observation on lattice fringes (Fig. 3c) reveal the presence of two different inter-planar spacing and their determined sizes of 0.285 and 0.328 nm are respectively attributed to the (1 0 1)
11541
Ceramics International 45 (2019) 11539–11548
S. Vasanthavel, et al.
Fig. 2. Raman spectra of Mn2+ doped ZrO2eSiO2 binary system powders recorded after heat treatment at different temperatures. Fig. 2a-c corresponds to the patterns at 900, 1000 and 1300 °C.
plane of t-ZrO2 and (2 0 0) plane of ZrSiO4. Nonetheless, lattice fringes typical of t-ZrO2 are mainly noticed and moreover SAED pattern (Fig. 3d) also portrays the planes respective of t-ZrO2 which infers good concurrence with the XRD results obtained at 900 °C that displayed tZrO2 as a dominant component. Further, the ability of ZrO2eSiO2 binary system to induce ZrSiO4 crystallization at 900 °C is also apparent as the lattice fringes typical of ZrSiO4 is also visible alongside t-ZrO2. The EDX spectra (Figure S2) confirms the presence of Zr, Si, Mn and O elements and their atomic ratios accords well with the precursor concentrations utilized during the synthesis.
3.4. Quantitative analysis The quantitative phase analysis and structural variations in ZrSiO4 due to manganese additions were determined from the Rietveld refinement of powder XRD patterns. The selective refined plots of 5MZS at 1000 °C and 30MZS at 1200 °C are presented in Fig. 4a and b, respectively. The refined data (Table 2) of PZS and 2.5MZS envisage
discrete t-ZrO2 while the SiO2 still remains amorphous at 1000 °C. The other MZS systems yield ZrSiO4 as a major component alongside t-ZrO2, m-ZrO2 and c-SiO2 as minor components at 1000 °C. For instance, 5MZS yield 84.00 wt% of ZrSiO4 while the other components contribute to the rest. Excluding 2.5MZS and 5MZS, the other MZS systems indicate a gradual upsurge in Mn2O3 content as a function of incremental Mn2+ additions. This observation enunciate the occupancy of manganese at either ZrO2 or SiO2 till 5 wt%, while the excess manganese oxidizes to form Mn2O3. However, the phase fractions of t-ZrO2, c-SiO2 and m-ZrO2 showed insignificant variations in the MZS systems irrespective of Mn2+ additions. Furthermore, negligible variations on lattice data of ZrSiO4 are also noticed notwithstanding the Mn2+ content. The data of 2.5MZS at 1100 °C (Table S1) enunciate ∼50 wt% tZrO2 while the phase fraction of ZrSiO4 and m-ZrO2 share equal propositions. A maximum of 85.00 wt % ZrSiO4 and minor amounts of ZrO2 and c-SiO2 is determined for 5MZS. The enriched phase content of ZrSiO4 in other MZS systems at 1100 °C is mainly attributed to the enhanced reaction kinetics between t-ZrO2 and c-SiO2 at this particular
11542
Ceramics International 45 (2019) 11539–11548
S. Vasanthavel, et al.
Fig. 3. TE micrographs of 5MZS obtained after heat treatment at 900 °C. The atomic composition derived from the EDX spectra for C, Cu, O, Si, Mn and Zr elements are respectively listed as 69.74, 4.27, 14.10, 5.09, 0.41 and 6.38 atom percent.
temperature. This inference is plausible based on the decline in weight fractions of t-ZrO2 and c-SiO2. Nevertheless, the existence of these phases is still detected in minor amounts at 1100 °C. PZS system shows 20 wt% of ZrSiO4 while 5MZS accounts for a maximum of 93 wt% ZrSiO4, alongside minor factions of t-ZrO2 and c-SiO2 at 1200 °C. Except 5MZS, other MZS compositions signify the enhanced ZrSiO4 formation alongside the progressive Mn2O3 content as a function of enhanced Mn2+ additions, demonstrating good similarities with the data obtained at 1100 °C. Furthermore, the complete absence of c-SiO2, alongside with relatively negligible factions of the t-ZrO2 and m-ZrO2, were detected for higher Mn2+ concentrations at 1200 °C. The ability of the ZrSiO4 lattice to accommodate Mn2+ is also determined through the refinement of occupancy values. The refined occupancy values at 1200 °C confirm Mn2+ occupancy at the ZrSiO4 lattice, as observed in case of 2.5MZS and 5MZS in the increasing order; however, negligible increases in the Mn2+ occupancy are noticed beyond 5MZS. The data obtained at 1300 °C perceived the sole presence of ZrSiO4 for 5MZS. While the trend on the phase fraction data of t-ZrO2 and m-ZrO2 were found similar in all the MZS compositions at 1300 °C. Nevertheless, relatively a minor enhancement in the phase content of Mn2O3 is obvious in 1300 °C when compared to the data obtained at 1200 °C. Generally, ZrSiO4 possesses tetragonal structure that crystallizes in I41/amd space setting. The co-ordination of Zr and Si atoms with O atom are respectively of 8-fold (ZrO8) and 4-fold (SiO4) in ZrSiO4 structure. This 8-fold co-ordination of ZrO8 is classified in two ZrO4 tetrahedra; one being elongated and other in a compressed state. The compressed ZrO4 tetrahedra share edges with SiO4 tetrahedra while the elongated ZrO4 tetrahedra possess free O atoms. Due to this unique feature, ZrSiO4 comprises two kind of ZreO bond distances; the shortest being the one that possess ZreOeSi co-ordination and the longest being
the Zr co-ordination with free oxygen atom. Table 3 compares the different bond lengths among standard ZrSiO4 27 and 5MZS composition that signified single phase ZrSiO4 at 1300 °C. A sizeable enhancement in ZreO1 and ZreO2 bond lengths are perceived in 5MZS in comparison with the standard ZrSiO4. Despite these variations, the SieO bond distance remains unperturbed in both the systems. The ZreO bond length variations are mainly attributed to the partial replacement of lower sized Mn2+ (0.67 Å) for higher sized Zr4+ (0.84 Å), which is expected to induce an overall contraction of the ZrSiO4 unit cell. Subsequently, the ZreO1 and ZreO2 bond lengths in 5MZS are increased due to the partial occupancy of Mn2+ for Zr4+. Moreover, the two dimensional Fourier maps of (2 0 0) and (1 1 2) planes along x axis (Fig. 5) direction also signifies the occupancy of Mn2+ at ZrSiO4 unit cell. The maps obtained at two different planes affirm the high charge distribution localized around Zr4+ atom followed by Si4+ and O2− atoms. 3.5. X-ray photoelectron (XPS) spectroscopy The XPS analysis is performed to determine the elemental states in ZrO2eSiO2 binary system due to manganese additions. The survey scan (Fig. 6a) depicts the peaks that correspond to the elements of Zr, Si, O and Mn along with the peak typical of carbon, which is an apparent contamination that arises during XPS analysis. Fig. 6b represents the Mn 2p3/2 peak centred at 640.2 eV and 2p1/2 peak centred at 651.7 eV with the energy difference of 12.2 eV. The deconvolution of 2p3/2 peak exhibit two bands at 640.1 and 642.4 eV, which are attributed to Mn2+ and Mn3+ oxidation states [38–40]. The 2p1/2 peak centred at 652.4 eV is distinctive of +3 oxidation state of manganese. Similarly, the energy difference of 12.2 eV between two splits is also credited to the Mn3+
11543
Ceramics International 45 (2019) 11539–11548
S. Vasanthavel, et al.
Fig. 4. Refined diffraction patterns of PZS at 1100 °C (Fig. 4a) 2.5MZS at 1100 °C (Fig. 4b) 5MZS at 1300 °C (Fig. 4c) and 30MZS at 1300 °C (Fig. 4d).
state of Mn2O3 [41,42]. 3.6. Colour illuminations The photographs of PZS and MZS powders heat treated at 1000 and 1300 °C are presented in Fig. 7. PZS powders at 1000 and 1300 °C were determined as white while MZS powders demonstrated a wide range of colours and moreover their intensity tends to progress towards dark contrast influenced by the combination of enhanced Mn additions and heat treatment temperatures. 2.5MZS at 1000 °C (Fig. 7a) deliver grey contrast and thereafter turns to light brown in 10MZS and further the depth in the colour contrast is witnessed in the order of 20MZS and 30MZS. Nevertheless, MZS at 1300 °C (Fig. 7b) perceived relatively intense tints with respect to their corresponding colour shades observed at 1000 °C. The reflectance spectra (Fig. 8) and corresponding L*, a* and b* values (Table 4) of MZS powders are presented. The reduction in L* values as a function of enhanced Mn content confirms the colour darkening while a reduction in a* values portray the shift of colour shades from red to green region. The decline in b* values demonstrate a gradual yellow to blue shift. Thus, the comparison of colour changes noticed in MZS and PZS is mainly influenced by the manganese content and their concentration. 4. Discussion The crucial role of Mn2+ doping in ZrO2eSiO2 binary system to favour ZrSiO4 formation at lower temperatures is evident from the investigation. This hypothesis is derived through an appropriate comparison with pure ZrO2eSiO2 binary oxide system that is persistent with
crystalline t-ZrO2 and amorphous SiO2 until 1100 °C. Generally, ZrSiO4 crystallization in pure ZrO2eSiO2 binary oxide system triggers at 1200 °C as evident from the current investigation and its transformation to unique phase occur at 1500 °C [43,44]. The plausible mechanism for the ZrSiO4 formation arises from the reaction between crystalline t-ZrO2 and amorphous SiO2 [43,44]. As witnessed from XRD, Raman and TEM analysis, ZrSiO4 crystallization is initiated at 900 °C with an appropriate dose of Mn2+ additions in the range of 5–20 wt%. The sluggishness of ZrSiO4 crystallization in case of low Mn2+ (2.5 wt%) and high Mn2+ (30 wt%) additions at 900 °C ensures the crucial role of dopant concentration to instigate ZrSiO4 formation at low temperatures. Nevertheless, the formation of ZrSiO4 in 2.5MZS and 30MZS alongside the presence of ZrSiO4 as a major component in all MZS systems at higher temperatures enunciate the importance of thermal energy in ZrSiO4 formation. Further, based on these observations, the crucial role of Mn2+ content to promote ZrSiO4 formation at low temperatures is deduced as follows. The negligence of Mn2O3 at low concentrations and its presence beyond 5 wt% endorse the accommodation of Mn2+ at the lattice sites of ZrSiO4. Beyond the occupancy limit of 5 wt%, Mn2+ oxidizes to stable Mn2O3 form and thus settles in the amorphous SiO2 matrix. This inference is validated by comparing the lattice parameters of ZrO2 in MZS and PZS systems. Nonetheless, amorphous nature of XRD patterns at 900 °C and their subsequent transformation to crystalline ZrSiO4 at 1000 °C restrain to gain consistent lattice changes in t-ZrO2. Instead, supportive evidence is gained from the refined lattice data of ZrSiO4, which displayed negligible changes in the structural parameters of ZrSiO4 despite incremental Mn2+ additions. Further, an additional inference is also accomplished from the XPS analysis that endorses the
11544
Ceramics International 45 (2019) 11539–11548
S. Vasanthavel, et al.
Table 2 Refined structural parameters of PZS and MZS systems heat treated at three different temperatures. 1000 °C Sample code
χ2
RBragg
Phase fraction (%) ZrSiO4
Mn2O3
t-ZrO2
m-ZrO2
c-SiO2
a = b axis
c- axis
– – – 5.00 8.00 11.00 13.00
100 100 5.00 4.00 5.00 8.00 8.00
– – 4.00 6.00 2.00 2.00 –
– – 7.00 10.00 6.00 6.00 7.00
3.5915(2)* 3.5943(1)* 6.6039(4) 6.6070(3) 6.6079(2) 6.6073(3) 6.6055(5)
5.1822(3)* 5.1833(2)* 5.9816(1) 5.9829(5) 5.9846(2) 5.9846(2) 5.9828(3)
t-ZrO2
m-ZrO2
c-SiO2
Lattice data of ZrSiO4 and t-ZrO2* a = b axis c- axis
76.00 4.00 6.00 3.00 1.00 1.00 1.00
3.00 3.00 – – – 3.00 3.00
– 5.00 – – – – –
– 6.6029(3) 6.6088(2) 6.6073(1) 6.5924(1) 6.6075(2) 6.6030(1)
t-ZrO2
m-ZrO2
SiO2
Lattice data of ZrSiO4 a = b axis c- axis
Occupancy
21.00 3.00 – 2.00 2.00 1.00 1.00
14.00 2.00 – – – 2.00 3.00
9.00 3.00 – – – – –
6.6123 6.6031(3) 6.6094(2) 6.6069(1) 6.6082(1) 6.6078(2) 6.6063(1)
− – 0.052 0.051 0.054 0.060 0.055
PZS 2.5MZS 05MZS 10MZS 15MZS 20MZS 30MZS
1.06 1.42 1.98 1.82 1.73 1.95 1.92
7.81 9.53 8.68 9.17 8.01 8.82 9.23
– – 84.00 75.00 79.00 73.00 72.00
1200 °C Sample code
χ2
RBragg
Phase fraction (%) ZrSiO4 Mn2O3 – – – 6.0 7.00 7.00 14.00
PZS 2.5MZS 05MZS 10MZS 15MZS 20MZS 30MZS
1.74 1.69 1.28 1.45 1.48 1.73 1.80
9.39 9.45 9.76 8.08 9.88 8.49 9.45
20.00 88.00 94.00 91.00 92.00 89.00 82.00
1300 °C Sample code
χ2
RBragg
Phase fraction (%) ZrSiO4 Mn2O3
PZS 2.5MZS 05MZS 10MZS 15MZS 20MZS 30MZS
1.90 1.73 1.18 1.90 1.98 1.94 1.31
9.37 8.78 8.87 9.91 9.60 9.87 8.63
Lattice data of ZrSiO4 and t-ZrO2*
58.00 92.00 100.00 89.00 87.00 84.00 81.00
– – – 8.0 11.00 13.00 15.00
Table 3 Selective bond lengths in standard ZrSiO427 and the refined 5MZS composition at 1300 °C. Bond length
ZrSiO4
5MZS
ZreO1 ZreO2 SieO
2.1303 2.2688 1.6223
2.1358 (4) 2.2835 (6) 1.6228 (2)
presence of both Mn2+ and Mn3+ states. The presence of Mn3+ is in good agreement with the measured Mn2O3 contents, whereas the +2 oxidation state is credited from the Mn2+ accommodation at the ZrSiO4 lattice. The lattice distortion of t-ZrO2 influenced by the dopant size is also considered a key factor to induce the reaction between t-ZrO2 and amorphous SiO2 at low temperatures. This fact garners support from the previous reports by the authors on rare earth element additions to ZrO2eSiO2 binary system [45-47]. Rare earth (RE) additions in ZrO2eSiO2 system ensure the accommodation of large sized dopants (> 0.9 Å) at the small sized Zr4+ (0.84 Å), which, as a consequence, favour the lattice expansion of t-ZrO2 and subsequent t → c-ZrO2 phase transition. The continuous lattice expansion of ZrO2, influenced by the larger sized rare earths restricts the crystallization of ZrSiO4. Moreover, this trend has been more clearly noticed for incremental rare earth additions alongside concomitant heat treatments until 1400 °C. On the contrary, lower sized dopants, namely Fe3+, V4+ and Ti4+, trigger ZrSiO4 crystallization from 1000 °C [9,15,48]. Further, the occupancy limit of these dopants in ZrSiO4 lattice were determined as ≤ 5 wt% and simultaneous lattice contraction is also reported. In a similar manner, the lower sized Mn2+ (0.67 Å) occupancy at ZrSiO4 lattice and the accommodation limit of ∼ 5 wt% is also determined from this
– 5.9800(2) 5.9848(3) 5.9839(1) 5.9713(1) 5.9832(1) 5.9797(1)
5.9686 5.9820(2) 5.9910(3) 5.9724(1) 5.9839(1) 5.9873(1) 5.9763(1)
investigation. Hence, the lattice contraction induced by Mn2+ occupancy at the t-ZrO2 lattice triggers reaction with amorphous SiO2 ≤ 1000 °C to yield ZrSiO4. The bond distance data and Fourier maps also support the partial replacement of lower sized Mn2+ for the higher sized Zr4+ to promote the crystallization of ZrSiO4. In other words, the lattice expansion of t-ZrO2, induced by dopants with larger ionic radii, as observed in rare earth additions, restrains the ZrSiO4 formation until 1400 °C. Mn2+ concentration and heat treatment temperatures play crucial role to instigate ZrSiO4 crystallization. A sole ZrSiO4 phase is accomplished only for the 5 wt% Mn2+ additions at 1300 °C while the formation of Mn2O3 beyond 5 wt% confines the complete ZrSiO4 formation. It is worthy to state that crystallization of sole ZrSiO4 is found negligible in pure ZrO2eSiO2 system till 1400 °C. The plausible reason for the lack of attainment of single phase ZrSiO4 is mainly due to the crystallization of amorphous SiO2 as c-SiO2, which also has caused partial t→m-ZrO2 phase degradation. It is worthy to mention that crystallization of c-SiO2 usually occurs at ∼1200 °C and thus restricts the reaction of t-ZrO2 with c-SiO2 at low temperatures. The obvious colour changes are induced by manganese and the enhanced colour intensity is also apparent for incremental Mn2+ additions. 5. Conclusion The deceive role of manganese additions on ZrSiO4 formation at low temperature is reported in the present investigation. Mn2+ prefers to occupy the lattice sites of t-ZrO2 and its occupancy limit is determined as 5 wt%. Preferential crystallization of Mn2O3 is determined for the manganese additions beyond 5 wt%. The substitution of small sized Mn2+ for the Zr4+ induce the lattice contraction in t-ZrO2, thus triggering the reaction of t-ZrO2 with amorphous SiO2 to yield ZrSiO4 at relatively low temperatures. The colour change of ZrSiO4 induced by
11545
Ceramics International 45 (2019) 11539–11548
S. Vasanthavel, et al.
Fig. 5. Fig. 5a depicts the crystal structure of 5MZS composition signifying the formation of ZrSiO4. Yellow and pink shaded portions respectively denote (2 0 0) and (1 1 2) planes. Fig. 5b and c represent 2D Fourier maps of (2 0 0) and (1 1 2) planes respectively. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
manganese is also determined.
Acknowledgments The financial assistance received from Council of Scientific and Industrial Research, CSIR (Reference: 01(2952)/18/EMR-II dated 01.05.2018) India is acknowledged. The facilities availed from Central
Instrumentation Facility (CIF) of Pondicherry University is also acknowledged. Dr. S. Vasanthavel acknowledges CSIR, India (Ref. No. 09/ 559(0121)/18-EMR-I) for Research Associate Fellowship and Mr. V. Ponnilavan acknowledges CSIR, India (Ref. No. 09/559(0114)/16EMR-I) for Senior Research Fellowship. This work was developed in the scope of the project CICECO−Aveiro Institute of Materials (Ref. FCT UID/CTM/50011/2013), financed by national funds through the FCT/
Fig. 6. XPS spectra of 20MZS (Fig. 6a: Survey scan; Fig. 6b: Mn 2p doublet peak) recorded after heat treatment at 1100 °C. 11546
Ceramics International 45 (2019) 11539–11548
S. Vasanthavel, et al.
Fig. 7. Photographs of PZS and MZS powders heat treated at (a) 1000 °C (b) 1300 °C.
Fig. 8. Reflectance spectra of MZS powders obtained after heat treatment at 1300 °C. Table 4 L*, a* and b* values of MZS samples obtained after heat treatment at 1300 °C. Sample code
5MZS
10MZS
20MZS
30MZS
L* a* b*
54.12 2.86 2.23
44.92 2.12 0.63
38.90 0.98 −0.42
34.98 0.45 −0.91
MEC and when applicable co-financed by FEDER under the PT2020 Partnership Agreement. Appendix A. Supplementary data Supplementary data to this article can be found online at https:// doi.org/10.1016/j.ceramint.2019.03.023. References [1] Y. Shi, X. Huang, D. Yan, Synthesis and characterization of ultrafine zircon powder, Ceram. Int. 24 (1998) 393–400. [2] T. Mori, H. Yamamura, H. Kobayashi, T. Mitamura, Preparation of high-purity ZrSiO4 powder using sol-gel processing and mechanical properties of the sintered body, J. Am. Ceram. Soc. 75 (1992) 2420–2426. [3] L. Rubio-Puzzo, M.C. Caracoche, M.M. Cervera, P.C. Rivas, A.M. Ferrari, F. Bondioli, Hyperfine characterization of pure and doped zircons, J. Solid State Chem. 150 (2000) 14–18. [4] C. Veytizou, J.F. Quinson, Y. Jorand, Preparation of zircon bodies from amorphous precursor powder synthesized by sol-gel processing, J. Eur. Ceram. Soc. 22 (2002) 2901–2909. [5] G. Vilmin, S. Komarneni, R. Roy, Lowering crystallization temperature of zircon by nanoheterogeneous sol-gel processing, J. Mater. Sci. 22 (1987) 3556–3560. [6] S. Ying, H. Xiaoxian, Y. Dongsheng, Effect of natural zircon powder as seeds on the
gel synthesis of zircon powder, Mater. Lett. 21 (1994) 79–83. [7] F.J. Berry, D. Eadon, J. Holloway, L.E. Smart, Iron-doped zirconium silicate Part 1. The location of iron, J. Mater. Chem. 6 (1996) 221–225. [8] G. Cappelletti, S. Ardizzone, P. Fermo, S. Gilardoni, The influence of iron content on the promotion of the zircon structure and the optical properties of pink coral pigments, J. Eur. Ceram. Soc. 25 (2005) 911–917. [9] S. Ardizzone, G. Cappelletti, P. Fermo, C. Oliva, M. Scavini, F. Scimè, Structural and spectroscopic investigations of blue, vanadium-doped ZrSiO4 pigments prepared by a sol-gel route, J. Phys. Chem. B 109 (2005) 22112–22119. [10] T. Demiray, D.K. Nath, F.A. Hummel, Zircon-vanadium blue pigment, J. Am. Ceram. Soc. 53 (1970) 1–4. [11] M. Trojan, Synthesis of a grey-brown zirconium silicate pigment, Ceram. Int. 16 (1990) 135–141. [12] N. Montoya, G. Herrera, J. Alarcon, Synthesis and characterization of praseodymium containing ZrSiO4 solid solutions from gels, Ceram. Int. 37 (2011) 3609–3616. [13] R.A. Eppler, Kinetics of formation of an iron-zircon pink color, J. Am. Ceram. Soc. 62 (1979) 47–49. [14] P. Tartaj, T. González-Carreño, C.J. Serna, M. Ocaña, Iron zircon pigments prepared by pyrolysis of aerosols, J. Solid State Chem. 128 (1997) 102–108. [15] R. Udaykiran, S. Vasanthavel, S. Kannan, Coordinative crystallization of ZrSiO4 and α-Fe2O3 composites and their resultant structural, morphological, and mechanical characteristics, Cryst. Growth Des. 15 (2015) 4075–4086. [16] J.A. Badenes, M. Llusar, J.B. Vicent, M.A. Tena, G. Monros, The nature of Pr-ZrSiO4 yellow ceramic pigment, J. Mater. Sci. 37 (2002) 1413–1420. [17] M. Ocaña, A. Caballero, A.R. González-Elipe, P. Tartaj, C.J. Serna, R.I. Merino, The effects of the NaF flux on the oxidation state and localisation of praseodymium in Pr-doped zircon pigments, J. Eur. Ceram. Soc. 19 (1999) 641–648. [18] M. Ocaña, A. Caballero, A.R. González-Elípe, P. Tartaj, C.J. Serna, Valence and localization of praseodymium in Pr-doped zircon, J. Solid State Chem. 139 (1998) 412–415. [19] M. Shoyama, H. Nasu, K. Kamiya, Preparation of rare earth-zircon pigments by the sol-gel method, J. Ceram. Soc. Japan. 106 (1998) 279–284. [20] A. Beltran, S. Bohm, A. Flores-Riveros, J.A. Igualada, G. Monros, J. Andres, V. Luana, A.M. Pendas, Ab initio cluster-in-the -lattice description of vanadiumdoped zircon. Analysis of the impurity centers V4+: ZrSiO4, J. Phys. Chem. 97 (1993) 2555–2559. [21] S. Di Gregorio, M. Greenblatt, J.H. Pifer, M.D. Sturge, An ESR and optical study of V4+ in zircon-type crystals, J. Chem. Phys. 76 (1982) 2931–2937. [22] M. Shoyama, N. Matsumoto, T. Hashimoto, H. Nasu, K. Kamiya, Sol-gel synthesis of zircon-effect of addition of lithium ions, J. Mater. Sci. 33 (1998) 4821–4828. [23] A. García Murillo, F. de J. Carrillo Romo, A.M. Torres Huerta, M.A. Domínguez Crespo, E. Ramírez Meneses, H. Terrones, A. Flores Vela, Microstructural evolution of the system Ni–ZrO2–SiO2 synthesized by the sol–gel process, J. Alloy. Comp. 495 (2010) 574–577. [24] S. Cava, S.M. Tebcherani, S.A. Pianaro, C.A. Paskocimas, E. Longo, J.A. Varela, Síntese e caracterização do sistema ZrO2-SiO2 com adição de cobalto para uso como pigmentos cerâmicos, Cerâmica 51 (2005) 302–307. [25] Q. Zhang, Q. Yang, Y. Sun, H. Wang, Low temperature synthesis of a new yellowish brown ceramic pigment based on FeNbO4@ZrSiO4, Ceram. Int. 44 (2018) 12621–12626. [26] B.H. Toby, A graphical user interface for GSAS, J. Appl. Crystallogr. 34 (2001) 210–213. [27] R.M. Hazen, L.M. Finger, Crystal structure and compressibility of zircon at high pressure, Am. Mineral. 64 (1979) 196–201. [28] R. Norrestam, a-Manganese (III) oxide–A C-type sesquioxide of orthorhombic symmetry, Acta Chem. Scand. 21 (1967) 2871–2884. [29] C.J. Howard, R.J. Hill, B.E. Reichert, Structures of ZrO2 polymorphs at room temperature by high-resolution neutron powder diffraction, Acta Crystallogr. Sect. B Struct. Sci. 44 (1988) 116–120. [30] D.K. Smith, W. Newkirk, The crystal structure of baddeleyite (monoclinic ZrO 2 ) and its relation to the polymorphism of ZrO 2, Acta Crystallogr. 18 (1965) 983–991. [31] P. Dera, J.D. Lazarz, V.B. Prakapenka, M. Barkley, R.T. Downs, New insights into the high-pressure polymorphism of SiO2 cristobalite, Phys. Chem. Miner. 38 (2011) 517–529. [32] S. Vasanthavel, S. Kannan, Phase stabilization of ZrO2 polymorph by combined
11547
Ceramics International 45 (2019) 11539–11548
S. Vasanthavel, et al.
[33]
[34] [35]
[36] [37] [38] [39]
[40] [41]
additions of Ca2+ and PO43- ions through an in situ synthetic approach, J. Am. Ceram. Soc. 97 (2014) 3774–3780. S. Vasanthavel, P. Nandha Kumar, S. Kannan, Quantitative analysis on the influence of SiO2 content on the phase behavior of ZrO2, J. Am. Ceram. Soc. 97 (2014) 635–642. C.M. Phillippi, K.S. Mazdiyasni, Infrared and Raman spectra of zirconia polymorphs, J. Am. Ceram. Soc. 54 (1971) 254–258. R. Udaykiran, S. Vasanthavel, S. Kannan, Coordinative crystallization of ZrSiO4 and α-Fe2O3 composites and their resultant structural, morphological, and mechanical characteristics, Cryst. Growth Des. 15 (2015) 4075–4086. 1372, P. Griffith, W.P.G.T.C. Soc, Raman Studies on Rock-Forming Minerals . Part I . O, (1969), pp. 1372–1377. P. Dawson, M.M. Hargreave, G.R. Wilkinson, The vibrational spectrum of zircon (ZrSiO4), J. Phys. C Solid State Phys. 4 (1971) 240–256. R.W.G. Syme, D.J. Lockwood, H.J. Kerr, Raman spectrum of synthetic zircon (ZrSiO4) and thorite (ThSiO4), J. Phys. C Solid State Phys. 10 (1977) 1335–1348. Z.H. Wang, D.Y. Geng, Y.J. Zhang, Z.D. Zhang, Morphology, structure and magnetic properties of single-crystal Mn3O4nanorods, J. Cryst. Growth 310 (2008) 4148–4151. M. Salavati-Niasari, F. Davar, Synthesis of monodisperse Mn3O4 nanocrystals, Int. J. Nanosci. 08 (2009) 281–283. J.W. Lee, A.S. Hall, J.-D. Kim, T.E. Mallouk, A facile and template-free
[42]
[43] [44] [45]
[46]
[47]
[48]
11548
hydrothermal synthesis of Mn3O4 nanorods on graphene sheets for supercapacitor electrodes with long cycle stability, Chem. Mater. 24 (2012) 1158–1164. A. Moses Ezhil Raj, S.G. Victoria, V.B. Jothy, C. Ravidhas, J. Wollschläger, M. Suendorf, M. Neumann, M. Jayachandran, C. Sanjeeviraja, XRD and XPS characterization of mixed valence Mn3O4 hausmannite thin films prepared by chemical spray pyrolysis technique, Appl. Surf. Sci. 256 (2010) 2920–2926. C. Veytizou, Zircon formation from amorphous silica and tetragonal zirconia: kinetic study and modelling, Solid State Ionics 139 (2001) 315–323. T. Itoh, Formation of polycrystalline zircon (ZrSiO4) from amorphous silica and amorphous zirconia, J. Cryst. Growth 125 (1992) 223–228. S. Vasanthavel, B. Derby, S. Kannan, Stabilization of a t-ZrO 2 polymorph in a glassy SiO2 matrix at elevated temperatures accomplished by ceria additions, Dalton Trans. 46 (2017) 6884–6893. S. Vasanthavel, B. Derby, S. Kannan, Tetragonal to cubic transformation of SiO2 -stabilized ZrO2 polymorph through dysprosium substitutions, Inorg. Chem. 56 (2017) 1273–1281. S. Vasanthavel, S. Awasthi, A. Dhayalan, B. Derby, S. Kannan, Structural, mechanical, imaging and in vitro evaluation of the combined effect of Gd 3+ and Dy 3+ in the ZrO2 –SiO2 binary system, Inorg. Chem. 57 (2018) 4602–4612. A.K. Yadav, V. Ponnilavan, S. Kannan, Crystallization of ZrSiO4 from a SiO2 –ZrO2 binary system: the concomitant effects of heat treatment temperature and TiO2 additions, Cryst. Growth Des. 16 (2016) 5493–5500.
Contents lists available at ScienceDirect
Ceramics International journal homepage: www.elsevier.com/locate/ceramint
Manganese induced ZrSiO4 crystallization from ZrO2eSiO2 binary oxide system
T
S. Vasanthavela, M. Ezhilana, V. Ponnilavana, J.M.F. Ferreirab, S. Kannana,∗ a b
Centre for Nanoscience and Technology, Pondicherry University, Puducherry, 605 014, India Department of Materials and Ceramics Engineering, University of Aveiro, CICECO, Aveiro, 3810 193, Portugal
A R T I C LE I N FO
A B S T R A C T
Keywords: Manganese Zircon Zirconia Silica Structure
The ability of manganese to induce early zircon (ZrSiO4) crystallization is investigated. An assorted range of manganese additions to the ZrO2eSiO2 binary system through a Sol-Gel approach is attempted to achieve ZrSiO4 formation at low temperatures. XRD analysis alongside complementary Rietveld refinement tool has been used to determine the propelling effect of manganese on the low temperature formation of ZrSiO4. The results revealed the ability of 5 wt% manganese to induce the ZrSiO4 formation at 900 °C through its occupancy at the ZrO2 lattice. The lattice substitution of Zr4+ by the lower sized Mn2+ and the concomitant lattice distortion of ZrO2 have been determined as the prime reason for manganese to enhance the reaction kinetics with amorphous SiO2 to yield ZrSiO4. Increments in the manganese content beyond 5 wt% are rejected by the ZrO2 lattice, making the excess to crystallize as Mn2O3. The colour change of ZrSiO4 is directly influenced by the manganese content in ZrO2eSiO2 binary system.
1. Introduction The salient features of low thermal conductivity, thermal shock resistance, high chemical stability and mechanical strength favour zircon (ZrSiO4) use in refractory industries [1–3]. ZrSiO4 derived from natural resources encompasses several impurities, which coupled with inadequate densification ability that restrict the potential technological applications. The synthetic ZrSiO4 derived from the combination of ZrO2 and SiO2 metal oxides is generally accomplished only at elevated heat treatments (> 1500 °C) that led to high manufacturing costs. Therefore, the low temperature synthesis of ZrSiO4 is a topic of interest for refractory industries. In this context, most of the studies envisage the aid of alkaline metal halides and alkaline metal nitrates as mineralizers to induce ZrSiO4 formation in the range of 1000–1200 °C [4–6]. Simultaneously, ZrSiO4 based pigments with tuneable colours have been widely developed by aiding different dopants as chromophores. Vanadium doped blue ZrSiO4, praseodymium doped yellow ZrSiO4 and iron doped pink ZrSiO4 are among the few that are commercially successful in pigment industries [7–12]. In this pursuit, many investigations were devoted to develop ZrSiO4 pigments at low temperature by the use of both dopants and mineralizers. Eppler et al. [13] emphasized the role of mineralizers to yield low temperature ZrSiO4 through the reaction between SiO2 and halides (H). The reaction between Si and halides yields SiH4 species and their migration over ZrO2 ∗
surface has been stated as reason to favour ZrSiO4 formation ∼1000 °C. Nonetheless, ZrSiO4 pigments have been developed at low temperatures only with the aid of dopants that act as chromophores. The literature evinces contradictory reports on the crucial role of dopants and their concentrations to promote of ZrSiO4 formation at low temperatures. In addition, the influence of chemical state of the dopants either in ionic or oxide forms to tune the resultant colour intensity is also poorly understood. In case of iron doped ZrSiO4, Tartaj et al. [14] emphasized the generation of oxygen vacancies in t-ZrO2 lattice by the occupancy of Fe3+ to favour ZrSiO4 nucleation, while the excess Fe3+ beyond the occupancy limit forms hematite (α-Fe2O3) and hence gets segregated throughout the ZrSiO4 matrix. The authors reported that Fe3+ additions till 5 wt% favour the ZrSiO4 formation by the reaction between Fe3+ substituted t-ZrO2 and amorphous SiO2, while the Fe3+ additions beyond 5 wt% crystallize as α-Fe2O3 under oxidative conditions [15]. The studies on praseodymium-doped ZrSiO4 by Badenes et al. [16] and Ocana et al. [17,18] emphasize the occupancy of Pr4+ at triangular dodecahedral sites of Zr4+. On the contrary, Shoyama et al. [19] reported the accommodation of Pr4+ at both triangular dodecahedral sites of Zr4+ and tetrahedral sites of Si4+ to favour ZrSiO4 formation. In a similar manner, the occupancy of vanadium (V4+) in vanadium doped ZrSiO4 systems is also contradictory with either dodecahedral sites of Zr4+ or distorted tetrahedral sites of Si4+ and the both sites [10,20,21].
Corresponding author. E-mail address: [email protected] (S. Kannan).
https://doi.org/10.1016/j.ceramint.2019.03.023 Received 10 December 2018; Received in revised form 27 February 2019; Accepted 5 March 2019 Available online 08 March 2019 0272-8842/ © 2019 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Ceramics International 45 (2019) 11539–11548
S. Vasanthavel, et al.
Further, the development of low temperature ZrSiO4 with other dopants such as Li+, Ni2+, Co2+, FeNbO4 and rare earth elements alongside different mineralizers were investigated and the results ensured the attainment of different colour pigments [22–25]. Nevertheless, the quest to attain unique ZrSiO4 phase at low temperature continues as most of the reported systems witnessed the presence of either ZrO2 (t/m-ZrO2) or cristobalite (c-SiO2) and/or other oxides as minor phases. In this context, the present study aims to investigate the inducing role of manganese in the formation of single phase ZrSiO4 at low temperatures from the ZrO2eSiO2 binary system. A detailed structural analysis is performed to gain quantitative information on the structural features of ZrSiO4 due to manganese additions. 2. Materials and methods 2.1. Powder synthesis Analytical grade zirconium oxychloride octahydrate [ZrOCl2.8H2O], tetra ethyl orthosilicate [(C2H5O)4Si, TEOS] and manganese (II) nitrate tetrahydrate [Mn(NO3)2.4H2O] were used as precursors for the sol-gel synthesis of the powders. Pure stoichiometric ZrO2eSiO2 binary system devoid of Mn2+ additions was prepared for comparative purposes. Compositions based on this ZrO2eSiO2 binary oxide system and containing progressive added amounts of manganese from 2.5 to 30 wt% with respect to the constant molar concentration of ZrO2 in the pure stoichiometric system were also prepared through the same sol-gel technique. The precursor molar concentrations along with their respective sample codes are reported in Table 1. In a brief description of the synthesis, individual stock solutions of ZrOCl2 and Mn(NO3)2 prepared in deionized water were mixed together under vigorous stirring conditions. TEOS solution dissolved in appropriate amount of C2H5OH was also separately prepared. Both solutions were mixed together and subsequently 0.1 M of HNO3 as a catalyst was added and the resultant mixture was allowed to stir until the formation of a precursor gel and thereafter dried at 120 °C overnight. The dried gel samples were grounded to fine powders and subjected to characterization studies after heat treatment at different temperatures with a dwell time for 2 h. 2.2. Powder characterization X-ray diffractometer (Rigaku, ULTIMA IV, Japan) was used to analyse the phase behaviour of powders using a CuKα radiation (k = 1.5406 Å) produced at 40 kV and 30 mA to scan the diffraction angles (2θ) between 10° and 70° with a step size of 0.02° 2θ per second. Standard ICDD (International Centre for Diffraction Data) Card Nos. 01083-1376 for ZrSiO4, 98-000-6458 for Mn2O3, 01-079-1765 for t-ZrO2, 01-083-0944 for m-ZrO2 and 00-076-0941 for cristobalite (c-SiO2) were used for the phase analysis of the powder XRD patterns. Raman spectrum of the powders were recorded using backscattering geometry of Confocal Raman microscope (Renishaw, Gloucestershire, UK) with an excitation wavelength of 785 nm by semiconductor diode laser (0.5% of Table 1 Precursors molar concentrations used for the powder synthesis. Sample code
ZrOCl2
(C2H5O)4Si
Mn(NO3)2
% of Mn2+ with respect to Zr4+
PZS 2.5 MZS 5 MZS 10 MZS 15 MZS 20 MZS 30 MZS
0.5 0.5 0.5 0.5 0.5 0.5 0.5
0.5 0.5 0.5 0.5 0.5 0.5 0.5
– 0.0125 0.025 0.05 0.075 0.10 0.15
– 2.5% 5% 10% 15% 20% 30%
* Denotes the lattice parameters of t-ZrO2.
power) and the data acquiring time of 30 s. The morphological features and selected area diffraction (SAED) patterns were recorded using high resolution transmission electron microscopy (HRTEM, TECNAI G2-F30 ST WIN, USA) associated with a silicon drift detector for energy dispersive X-ray spectroscopy (EDX) analysis. X-ray photoelectron spectroscopy (XPS) technique has been used for the analysis of compositional and chemical state of manganese. XPS was obtained using X-ray Photoelectron spectrometer (ULVAC-PHI, Japan). The binding energy calibrations for the shift in charge were calibrated using the C 1s peak of graphitic carbon (BE = 284.8 eV) setting as standard and binding energy background subtraction was carried out prior to the simulation using Gaussian function. Rietveld refinement of the powder XRD patterns were performed through GSAS-EXPGUI software package [26]. The standard crystallographic data were obtained from American mineralogist crystal structure database for the refinement of ZrSiO4, Mn2O3, t-ZrO2, m-ZrO2 and c-SiO2 as reported by Hazen et al., Norrestam et al., Howard et al., Smith et al. and Dera et al. respectively [27–31]. The Fourier charge density maps obtained from GSAS were viewed with VESTA. The reflectance spectra and corresponding L*, a* and b* parameters for the MZS samples were recorded using Premier colorscan instrument (A5000 model, Navi Mumbai, India). L* indicates the colour lightness (100 for white and 0 for black), a* indicates green (−)/red (+) region and b* denotes the blue (−)/yellow (+) region. 3. Results 3.1. Phase analysis The phase analysis of the pristine and assorted range of manganese additions in ZrO2eSiO2 binary system was determined through X-ray diffraction technique. The XRD patterns of the samples heat treated at 900 °C are displayed in Fig. 1a. The pure ZrO2eSiO2 (PZS) composition confirms the crystallization of single t-ZrO2 phase, while the Mn2+doped compositions (MZS) also ensure t-ZrO2 as being the major crystalline phase. The X-ray reflections of ZrO2eSiO2 system with 2.5 wt% of Mn additions enable to infer about the formation of t-ZrO2 as single phase, similarly to what was observed for PZS, while minor reflections typical of ZrSiO4 seem evident in the composition with 5 wt% of Mn, which tend to intensify upon increasing the Mn content to 10 wt%. The upsurge of Mn2O3 reflections is initially noticed in 10 wt% of Mn and thereafter a progressive intensity is noticed with respect to the increment in Mn additions. A concomitant decline in the intensity of X-ray reflections of ZrSiO4 is witnessed for progressive Mn additions. Moreover, an irregular trend in t- → m-ZrO2 phase transition is also noticed for the intermediate compositions (10MZS and 15MZS). The XRD patterns of the investigated compositions exhibit good consistency with their corresponding standard ICDD patterns respective of t-ZrO2, ZrSiO4 and Mn2O3. For the samples heat treated at 1000 °C, the XRD patterns (Fig. 1b) reveal the presence of single t-ZrO2 phase for PZS and 2.5MZS, while reflections of ZrSiO4 as dominant crystalline phase are witnessed in the remaining MZS compositions. The progressive increasing intensity trend of Mn2O3 reflections with incremental Mn2+ concentrations noticed at 900 °C is also replicated at 1000 °C. Moreover, t-ZrO2 and cristobalite (c-SiO2) are also determined as minor phases in the compositions with incremental Mn additions. With further increasing the heat treatment temperature to 1100 °C (Figure S1), the crystallization of ZrSiO4 is already obvious for 2.5MZS, whereas the XRD patterns of other MZS compositions displayed a good cohesion with the trend observed at 1000 °C. The XRD patterns obtained at 1200 °C (Fig. 1c) ensure the manifestation of ZrSiO4 in PZS sample. Despite the ZrSiO4 formation, t-ZrO2 is determined as a dominant component in PZS alongside a minor level of t→m-ZrO2 phase transition at 1200 °C. In terms of MZS, reflections typical of t-ZrO2 and c-SiO2 are observed in minor level for 2.5MZS and thereafter a gradual decline in their reflections is noticed for the incremental Mn2+ concentrations. On the
11540
Ceramics International 45 (2019) 11539–11548
S. Vasanthavel, et al.
Fig. 1. XRD patterns of PZS and Mn2+ doped ZrO2eSiO2 binary system recorded after heat treatment at different temperatures. Fig. 1a-d correspond to the patterns recorded respectively at 900, 1000, 1200 and 1300 °C.
contrary, the reflections distinctive of Mn2O3 demonstrate a gradual upsurge from 10MZS with respect to the incremental Mn2+ concentrations. PZS infers the presence of dominant ZrSiO4 at 1300 °C (Fig. 1d) alongside t-ZrO2, m-ZrO2 and c-SiO2 components complimented by their corresponding minor reflections. On the other hand, 5MZS ensured the formation of ZrSiO4 as a single phase at 1300 °C, while the other MZS compositions replicated the similar trend of 1200 °C. 3.2. Raman spectroscopy The Raman spectra recorded at 900 °C (Fig. 2a) exhibit good coherence with their corresponding XRD patterns. 2.5MZS showed the bands typical of t-ZrO2 while 5MZS, 10MZS and 15MZS confirm the combination of t-ZrO2 and ZrSiO4 bands at 900 °C. The bands observed at 148, 270, 317, 353, 456, 641 cm−1 are attributed to t-ZrO2 [32–34] while the 976 and 1008 cm−1 bands are assigned to symmetric ν1(SiO4) stretching and antisymmetric ν3(SiO4) stretching vibrations of ZrSiO4 [35–37]. Nonetheless, the other bands typical of ZrSiO4 at lower frequencies are negligible in 5MZS due to the dominant nature of t-ZrO2 at 900 °C. The progressive surge in the intensity of distinct ZrSiO4 bands, together with the simultaneous decline in t-ZrO2 bands are inevitable in 10MZS and 15MZS. Moreover, the characteristic ZrSiO4 bands at lower frequencies emerge from 10MZS and are more evident in 15MZS, which are in good agreement with the XRD results. The lower frequency bands at 202, 214, and 225 cm−1 are attributed to the vibrations amongst Zr4+ and SiO4 tetrahedron while 356 and 439 cm−1 bands is signposted for ν2(SiO4) antisymmetric bending and ν2(SiO4) symmetric bending vibrations, respectively. The less intense 393 cm−1 band is hardly
reported as an internal lattice vibration of ZrSiO4. The bands typical of t-ZrO2 and ZrSiO4 are barely visible in 20MZS and 30MZS and further the Raman bands corresponding to Mn2O3 are found negligible in all the MZS systems at 900 °C. The Raman spectra of 2.5MZS at 1000 °C (Fig. 2b) display the presence of typical t-ZrO2 bands while the distinct ZrSiO4 vibrations alongside a discrete 279 cm−1 band respective of t-ZrO2 is determined for 5MZS. The other common bands of t-ZrO2 are barely found in 5MZS while the remaining MZS systems signify the complete absence of tZrO2 bands. This contradicts the results gathered by XRD pointing out to the presence of ZrO2 (t/m-ZrO2) traces. The absence of distinct ZrO2 bands is mainly attributed to the high intensity ZrSiO4 bands. However, the reduced intensity of ZrSiO4 bands is also observed for the incremental Mn2+ additions. Moreover, the absence of typical Mn2O3 bands is evident at both 900 and 1000 °C. Similar to the XRD results, the Raman spectra recorded at 1300 °C (Fig. 2c) enunciate the formation of sole ZrSiO4 vibrations in case of 5MZS. While other MZS compositions also perceived a similar result of dominant ZrSiO4 vibrations; however, the negligence to detect typical Mn2O3 bands in these compositions at 1300 °C is mainly complimented by the dominant ZrSiO4 that intend to suppress vibrations pertinent to Mn2O3 and other minor phases. 3.3. Transmission electron microscopy Transmission electron micrographs of 5MZS heat treated at 900 °C (Fig. 3a and b) depict the distribution of crystalline fringes in an amorphous matrix. A close observation on lattice fringes (Fig. 3c) reveal the presence of two different inter-planar spacing and their determined sizes of 0.285 and 0.328 nm are respectively attributed to the (1 0 1)
11541
Ceramics International 45 (2019) 11539–11548
S. Vasanthavel, et al.
Fig. 2. Raman spectra of Mn2+ doped ZrO2eSiO2 binary system powders recorded after heat treatment at different temperatures. Fig. 2a-c corresponds to the patterns at 900, 1000 and 1300 °C.
plane of t-ZrO2 and (2 0 0) plane of ZrSiO4. Nonetheless, lattice fringes typical of t-ZrO2 are mainly noticed and moreover SAED pattern (Fig. 3d) also portrays the planes respective of t-ZrO2 which infers good concurrence with the XRD results obtained at 900 °C that displayed tZrO2 as a dominant component. Further, the ability of ZrO2eSiO2 binary system to induce ZrSiO4 crystallization at 900 °C is also apparent as the lattice fringes typical of ZrSiO4 is also visible alongside t-ZrO2. The EDX spectra (Figure S2) confirms the presence of Zr, Si, Mn and O elements and their atomic ratios accords well with the precursor concentrations utilized during the synthesis.
3.4. Quantitative analysis The quantitative phase analysis and structural variations in ZrSiO4 due to manganese additions were determined from the Rietveld refinement of powder XRD patterns. The selective refined plots of 5MZS at 1000 °C and 30MZS at 1200 °C are presented in Fig. 4a and b, respectively. The refined data (Table 2) of PZS and 2.5MZS envisage
discrete t-ZrO2 while the SiO2 still remains amorphous at 1000 °C. The other MZS systems yield ZrSiO4 as a major component alongside t-ZrO2, m-ZrO2 and c-SiO2 as minor components at 1000 °C. For instance, 5MZS yield 84.00 wt% of ZrSiO4 while the other components contribute to the rest. Excluding 2.5MZS and 5MZS, the other MZS systems indicate a gradual upsurge in Mn2O3 content as a function of incremental Mn2+ additions. This observation enunciate the occupancy of manganese at either ZrO2 or SiO2 till 5 wt%, while the excess manganese oxidizes to form Mn2O3. However, the phase fractions of t-ZrO2, c-SiO2 and m-ZrO2 showed insignificant variations in the MZS systems irrespective of Mn2+ additions. Furthermore, negligible variations on lattice data of ZrSiO4 are also noticed notwithstanding the Mn2+ content. The data of 2.5MZS at 1100 °C (Table S1) enunciate ∼50 wt% tZrO2 while the phase fraction of ZrSiO4 and m-ZrO2 share equal propositions. A maximum of 85.00 wt % ZrSiO4 and minor amounts of ZrO2 and c-SiO2 is determined for 5MZS. The enriched phase content of ZrSiO4 in other MZS systems at 1100 °C is mainly attributed to the enhanced reaction kinetics between t-ZrO2 and c-SiO2 at this particular
11542
Ceramics International 45 (2019) 11539–11548
S. Vasanthavel, et al.
Fig. 3. TE micrographs of 5MZS obtained after heat treatment at 900 °C. The atomic composition derived from the EDX spectra for C, Cu, O, Si, Mn and Zr elements are respectively listed as 69.74, 4.27, 14.10, 5.09, 0.41 and 6.38 atom percent.
temperature. This inference is plausible based on the decline in weight fractions of t-ZrO2 and c-SiO2. Nevertheless, the existence of these phases is still detected in minor amounts at 1100 °C. PZS system shows 20 wt% of ZrSiO4 while 5MZS accounts for a maximum of 93 wt% ZrSiO4, alongside minor factions of t-ZrO2 and c-SiO2 at 1200 °C. Except 5MZS, other MZS compositions signify the enhanced ZrSiO4 formation alongside the progressive Mn2O3 content as a function of enhanced Mn2+ additions, demonstrating good similarities with the data obtained at 1100 °C. Furthermore, the complete absence of c-SiO2, alongside with relatively negligible factions of the t-ZrO2 and m-ZrO2, were detected for higher Mn2+ concentrations at 1200 °C. The ability of the ZrSiO4 lattice to accommodate Mn2+ is also determined through the refinement of occupancy values. The refined occupancy values at 1200 °C confirm Mn2+ occupancy at the ZrSiO4 lattice, as observed in case of 2.5MZS and 5MZS in the increasing order; however, negligible increases in the Mn2+ occupancy are noticed beyond 5MZS. The data obtained at 1300 °C perceived the sole presence of ZrSiO4 for 5MZS. While the trend on the phase fraction data of t-ZrO2 and m-ZrO2 were found similar in all the MZS compositions at 1300 °C. Nevertheless, relatively a minor enhancement in the phase content of Mn2O3 is obvious in 1300 °C when compared to the data obtained at 1200 °C. Generally, ZrSiO4 possesses tetragonal structure that crystallizes in I41/amd space setting. The co-ordination of Zr and Si atoms with O atom are respectively of 8-fold (ZrO8) and 4-fold (SiO4) in ZrSiO4 structure. This 8-fold co-ordination of ZrO8 is classified in two ZrO4 tetrahedra; one being elongated and other in a compressed state. The compressed ZrO4 tetrahedra share edges with SiO4 tetrahedra while the elongated ZrO4 tetrahedra possess free O atoms. Due to this unique feature, ZrSiO4 comprises two kind of ZreO bond distances; the shortest being the one that possess ZreOeSi co-ordination and the longest being
the Zr co-ordination with free oxygen atom. Table 3 compares the different bond lengths among standard ZrSiO4 27 and 5MZS composition that signified single phase ZrSiO4 at 1300 °C. A sizeable enhancement in ZreO1 and ZreO2 bond lengths are perceived in 5MZS in comparison with the standard ZrSiO4. Despite these variations, the SieO bond distance remains unperturbed in both the systems. The ZreO bond length variations are mainly attributed to the partial replacement of lower sized Mn2+ (0.67 Å) for higher sized Zr4+ (0.84 Å), which is expected to induce an overall contraction of the ZrSiO4 unit cell. Subsequently, the ZreO1 and ZreO2 bond lengths in 5MZS are increased due to the partial occupancy of Mn2+ for Zr4+. Moreover, the two dimensional Fourier maps of (2 0 0) and (1 1 2) planes along x axis (Fig. 5) direction also signifies the occupancy of Mn2+ at ZrSiO4 unit cell. The maps obtained at two different planes affirm the high charge distribution localized around Zr4+ atom followed by Si4+ and O2− atoms. 3.5. X-ray photoelectron (XPS) spectroscopy The XPS analysis is performed to determine the elemental states in ZrO2eSiO2 binary system due to manganese additions. The survey scan (Fig. 6a) depicts the peaks that correspond to the elements of Zr, Si, O and Mn along with the peak typical of carbon, which is an apparent contamination that arises during XPS analysis. Fig. 6b represents the Mn 2p3/2 peak centred at 640.2 eV and 2p1/2 peak centred at 651.7 eV with the energy difference of 12.2 eV. The deconvolution of 2p3/2 peak exhibit two bands at 640.1 and 642.4 eV, which are attributed to Mn2+ and Mn3+ oxidation states [38–40]. The 2p1/2 peak centred at 652.4 eV is distinctive of +3 oxidation state of manganese. Similarly, the energy difference of 12.2 eV between two splits is also credited to the Mn3+
11543
Ceramics International 45 (2019) 11539–11548
S. Vasanthavel, et al.
Fig. 4. Refined diffraction patterns of PZS at 1100 °C (Fig. 4a) 2.5MZS at 1100 °C (Fig. 4b) 5MZS at 1300 °C (Fig. 4c) and 30MZS at 1300 °C (Fig. 4d).
state of Mn2O3 [41,42]. 3.6. Colour illuminations The photographs of PZS and MZS powders heat treated at 1000 and 1300 °C are presented in Fig. 7. PZS powders at 1000 and 1300 °C were determined as white while MZS powders demonstrated a wide range of colours and moreover their intensity tends to progress towards dark contrast influenced by the combination of enhanced Mn additions and heat treatment temperatures. 2.5MZS at 1000 °C (Fig. 7a) deliver grey contrast and thereafter turns to light brown in 10MZS and further the depth in the colour contrast is witnessed in the order of 20MZS and 30MZS. Nevertheless, MZS at 1300 °C (Fig. 7b) perceived relatively intense tints with respect to their corresponding colour shades observed at 1000 °C. The reflectance spectra (Fig. 8) and corresponding L*, a* and b* values (Table 4) of MZS powders are presented. The reduction in L* values as a function of enhanced Mn content confirms the colour darkening while a reduction in a* values portray the shift of colour shades from red to green region. The decline in b* values demonstrate a gradual yellow to blue shift. Thus, the comparison of colour changes noticed in MZS and PZS is mainly influenced by the manganese content and their concentration. 4. Discussion The crucial role of Mn2+ doping in ZrO2eSiO2 binary system to favour ZrSiO4 formation at lower temperatures is evident from the investigation. This hypothesis is derived through an appropriate comparison with pure ZrO2eSiO2 binary oxide system that is persistent with
crystalline t-ZrO2 and amorphous SiO2 until 1100 °C. Generally, ZrSiO4 crystallization in pure ZrO2eSiO2 binary oxide system triggers at 1200 °C as evident from the current investigation and its transformation to unique phase occur at 1500 °C [43,44]. The plausible mechanism for the ZrSiO4 formation arises from the reaction between crystalline t-ZrO2 and amorphous SiO2 [43,44]. As witnessed from XRD, Raman and TEM analysis, ZrSiO4 crystallization is initiated at 900 °C with an appropriate dose of Mn2+ additions in the range of 5–20 wt%. The sluggishness of ZrSiO4 crystallization in case of low Mn2+ (2.5 wt%) and high Mn2+ (30 wt%) additions at 900 °C ensures the crucial role of dopant concentration to instigate ZrSiO4 formation at low temperatures. Nevertheless, the formation of ZrSiO4 in 2.5MZS and 30MZS alongside the presence of ZrSiO4 as a major component in all MZS systems at higher temperatures enunciate the importance of thermal energy in ZrSiO4 formation. Further, based on these observations, the crucial role of Mn2+ content to promote ZrSiO4 formation at low temperatures is deduced as follows. The negligence of Mn2O3 at low concentrations and its presence beyond 5 wt% endorse the accommodation of Mn2+ at the lattice sites of ZrSiO4. Beyond the occupancy limit of 5 wt%, Mn2+ oxidizes to stable Mn2O3 form and thus settles in the amorphous SiO2 matrix. This inference is validated by comparing the lattice parameters of ZrO2 in MZS and PZS systems. Nonetheless, amorphous nature of XRD patterns at 900 °C and their subsequent transformation to crystalline ZrSiO4 at 1000 °C restrain to gain consistent lattice changes in t-ZrO2. Instead, supportive evidence is gained from the refined lattice data of ZrSiO4, which displayed negligible changes in the structural parameters of ZrSiO4 despite incremental Mn2+ additions. Further, an additional inference is also accomplished from the XPS analysis that endorses the
11544
Ceramics International 45 (2019) 11539–11548
S. Vasanthavel, et al.
Table 2 Refined structural parameters of PZS and MZS systems heat treated at three different temperatures. 1000 °C Sample code
χ2
RBragg
Phase fraction (%) ZrSiO4
Mn2O3
t-ZrO2
m-ZrO2
c-SiO2
a = b axis
c- axis
– – – 5.00 8.00 11.00 13.00
100 100 5.00 4.00 5.00 8.00 8.00
– – 4.00 6.00 2.00 2.00 –
– – 7.00 10.00 6.00 6.00 7.00
3.5915(2)* 3.5943(1)* 6.6039(4) 6.6070(3) 6.6079(2) 6.6073(3) 6.6055(5)
5.1822(3)* 5.1833(2)* 5.9816(1) 5.9829(5) 5.9846(2) 5.9846(2) 5.9828(3)
t-ZrO2
m-ZrO2
c-SiO2
Lattice data of ZrSiO4 and t-ZrO2* a = b axis c- axis
76.00 4.00 6.00 3.00 1.00 1.00 1.00
3.00 3.00 – – – 3.00 3.00
– 5.00 – – – – –
– 6.6029(3) 6.6088(2) 6.6073(1) 6.5924(1) 6.6075(2) 6.6030(1)
t-ZrO2
m-ZrO2
SiO2
Lattice data of ZrSiO4 a = b axis c- axis
Occupancy
21.00 3.00 – 2.00 2.00 1.00 1.00
14.00 2.00 – – – 2.00 3.00
9.00 3.00 – – – – –
6.6123 6.6031(3) 6.6094(2) 6.6069(1) 6.6082(1) 6.6078(2) 6.6063(1)
− – 0.052 0.051 0.054 0.060 0.055
PZS 2.5MZS 05MZS 10MZS 15MZS 20MZS 30MZS
1.06 1.42 1.98 1.82 1.73 1.95 1.92
7.81 9.53 8.68 9.17 8.01 8.82 9.23
– – 84.00 75.00 79.00 73.00 72.00
1200 °C Sample code
χ2
RBragg
Phase fraction (%) ZrSiO4 Mn2O3 – – – 6.0 7.00 7.00 14.00
PZS 2.5MZS 05MZS 10MZS 15MZS 20MZS 30MZS
1.74 1.69 1.28 1.45 1.48 1.73 1.80
9.39 9.45 9.76 8.08 9.88 8.49 9.45
20.00 88.00 94.00 91.00 92.00 89.00 82.00
1300 °C Sample code
χ2
RBragg
Phase fraction (%) ZrSiO4 Mn2O3
PZS 2.5MZS 05MZS 10MZS 15MZS 20MZS 30MZS
1.90 1.73 1.18 1.90 1.98 1.94 1.31
9.37 8.78 8.87 9.91 9.60 9.87 8.63
Lattice data of ZrSiO4 and t-ZrO2*
58.00 92.00 100.00 89.00 87.00 84.00 81.00
– – – 8.0 11.00 13.00 15.00
Table 3 Selective bond lengths in standard ZrSiO427 and the refined 5MZS composition at 1300 °C. Bond length
ZrSiO4
5MZS
ZreO1 ZreO2 SieO
2.1303 2.2688 1.6223
2.1358 (4) 2.2835 (6) 1.6228 (2)
presence of both Mn2+ and Mn3+ states. The presence of Mn3+ is in good agreement with the measured Mn2O3 contents, whereas the +2 oxidation state is credited from the Mn2+ accommodation at the ZrSiO4 lattice. The lattice distortion of t-ZrO2 influenced by the dopant size is also considered a key factor to induce the reaction between t-ZrO2 and amorphous SiO2 at low temperatures. This fact garners support from the previous reports by the authors on rare earth element additions to ZrO2eSiO2 binary system [45-47]. Rare earth (RE) additions in ZrO2eSiO2 system ensure the accommodation of large sized dopants (> 0.9 Å) at the small sized Zr4+ (0.84 Å), which, as a consequence, favour the lattice expansion of t-ZrO2 and subsequent t → c-ZrO2 phase transition. The continuous lattice expansion of ZrO2, influenced by the larger sized rare earths restricts the crystallization of ZrSiO4. Moreover, this trend has been more clearly noticed for incremental rare earth additions alongside concomitant heat treatments until 1400 °C. On the contrary, lower sized dopants, namely Fe3+, V4+ and Ti4+, trigger ZrSiO4 crystallization from 1000 °C [9,15,48]. Further, the occupancy limit of these dopants in ZrSiO4 lattice were determined as ≤ 5 wt% and simultaneous lattice contraction is also reported. In a similar manner, the lower sized Mn2+ (0.67 Å) occupancy at ZrSiO4 lattice and the accommodation limit of ∼ 5 wt% is also determined from this
– 5.9800(2) 5.9848(3) 5.9839(1) 5.9713(1) 5.9832(1) 5.9797(1)
5.9686 5.9820(2) 5.9910(3) 5.9724(1) 5.9839(1) 5.9873(1) 5.9763(1)
investigation. Hence, the lattice contraction induced by Mn2+ occupancy at the t-ZrO2 lattice triggers reaction with amorphous SiO2 ≤ 1000 °C to yield ZrSiO4. The bond distance data and Fourier maps also support the partial replacement of lower sized Mn2+ for the higher sized Zr4+ to promote the crystallization of ZrSiO4. In other words, the lattice expansion of t-ZrO2, induced by dopants with larger ionic radii, as observed in rare earth additions, restrains the ZrSiO4 formation until 1400 °C. Mn2+ concentration and heat treatment temperatures play crucial role to instigate ZrSiO4 crystallization. A sole ZrSiO4 phase is accomplished only for the 5 wt% Mn2+ additions at 1300 °C while the formation of Mn2O3 beyond 5 wt% confines the complete ZrSiO4 formation. It is worthy to state that crystallization of sole ZrSiO4 is found negligible in pure ZrO2eSiO2 system till 1400 °C. The plausible reason for the lack of attainment of single phase ZrSiO4 is mainly due to the crystallization of amorphous SiO2 as c-SiO2, which also has caused partial t→m-ZrO2 phase degradation. It is worthy to mention that crystallization of c-SiO2 usually occurs at ∼1200 °C and thus restricts the reaction of t-ZrO2 with c-SiO2 at low temperatures. The obvious colour changes are induced by manganese and the enhanced colour intensity is also apparent for incremental Mn2+ additions. 5. Conclusion The deceive role of manganese additions on ZrSiO4 formation at low temperature is reported in the present investigation. Mn2+ prefers to occupy the lattice sites of t-ZrO2 and its occupancy limit is determined as 5 wt%. Preferential crystallization of Mn2O3 is determined for the manganese additions beyond 5 wt%. The substitution of small sized Mn2+ for the Zr4+ induce the lattice contraction in t-ZrO2, thus triggering the reaction of t-ZrO2 with amorphous SiO2 to yield ZrSiO4 at relatively low temperatures. The colour change of ZrSiO4 induced by
11545
Ceramics International 45 (2019) 11539–11548
S. Vasanthavel, et al.
Fig. 5. Fig. 5a depicts the crystal structure of 5MZS composition signifying the formation of ZrSiO4. Yellow and pink shaded portions respectively denote (2 0 0) and (1 1 2) planes. Fig. 5b and c represent 2D Fourier maps of (2 0 0) and (1 1 2) planes respectively. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
manganese is also determined.
Acknowledgments The financial assistance received from Council of Scientific and Industrial Research, CSIR (Reference: 01(2952)/18/EMR-II dated 01.05.2018) India is acknowledged. The facilities availed from Central
Instrumentation Facility (CIF) of Pondicherry University is also acknowledged. Dr. S. Vasanthavel acknowledges CSIR, India (Ref. No. 09/ 559(0121)/18-EMR-I) for Research Associate Fellowship and Mr. V. Ponnilavan acknowledges CSIR, India (Ref. No. 09/559(0114)/16EMR-I) for Senior Research Fellowship. This work was developed in the scope of the project CICECO−Aveiro Institute of Materials (Ref. FCT UID/CTM/50011/2013), financed by national funds through the FCT/
Fig. 6. XPS spectra of 20MZS (Fig. 6a: Survey scan; Fig. 6b: Mn 2p doublet peak) recorded after heat treatment at 1100 °C. 11546
Ceramics International 45 (2019) 11539–11548
S. Vasanthavel, et al.
Fig. 7. Photographs of PZS and MZS powders heat treated at (a) 1000 °C (b) 1300 °C.
Fig. 8. Reflectance spectra of MZS powders obtained after heat treatment at 1300 °C. Table 4 L*, a* and b* values of MZS samples obtained after heat treatment at 1300 °C. Sample code
5MZS
10MZS
20MZS
30MZS
L* a* b*
54.12 2.86 2.23
44.92 2.12 0.63
38.90 0.98 −0.42
34.98 0.45 −0.91
MEC and when applicable co-financed by FEDER under the PT2020 Partnership Agreement. Appendix A. Supplementary data Supplementary data to this article can be found online at https:// doi.org/10.1016/j.ceramint.2019.03.023. References [1] Y. Shi, X. Huang, D. Yan, Synthesis and characterization of ultrafine zircon powder, Ceram. Int. 24 (1998) 393–400. [2] T. Mori, H. Yamamura, H. Kobayashi, T. Mitamura, Preparation of high-purity ZrSiO4 powder using sol-gel processing and mechanical properties of the sintered body, J. Am. Ceram. Soc. 75 (1992) 2420–2426. [3] L. Rubio-Puzzo, M.C. Caracoche, M.M. Cervera, P.C. Rivas, A.M. Ferrari, F. Bondioli, Hyperfine characterization of pure and doped zircons, J. Solid State Chem. 150 (2000) 14–18. [4] C. Veytizou, J.F. Quinson, Y. Jorand, Preparation of zircon bodies from amorphous precursor powder synthesized by sol-gel processing, J. Eur. Ceram. Soc. 22 (2002) 2901–2909. [5] G. Vilmin, S. Komarneni, R. Roy, Lowering crystallization temperature of zircon by nanoheterogeneous sol-gel processing, J. Mater. Sci. 22 (1987) 3556–3560. [6] S. Ying, H. Xiaoxian, Y. Dongsheng, Effect of natural zircon powder as seeds on the
gel synthesis of zircon powder, Mater. Lett. 21 (1994) 79–83. [7] F.J. Berry, D. Eadon, J. Holloway, L.E. Smart, Iron-doped zirconium silicate Part 1. The location of iron, J. Mater. Chem. 6 (1996) 221–225. [8] G. Cappelletti, S. Ardizzone, P. Fermo, S. Gilardoni, The influence of iron content on the promotion of the zircon structure and the optical properties of pink coral pigments, J. Eur. Ceram. Soc. 25 (2005) 911–917. [9] S. Ardizzone, G. Cappelletti, P. Fermo, C. Oliva, M. Scavini, F. Scimè, Structural and spectroscopic investigations of blue, vanadium-doped ZrSiO4 pigments prepared by a sol-gel route, J. Phys. Chem. B 109 (2005) 22112–22119. [10] T. Demiray, D.K. Nath, F.A. Hummel, Zircon-vanadium blue pigment, J. Am. Ceram. Soc. 53 (1970) 1–4. [11] M. Trojan, Synthesis of a grey-brown zirconium silicate pigment, Ceram. Int. 16 (1990) 135–141. [12] N. Montoya, G. Herrera, J. Alarcon, Synthesis and characterization of praseodymium containing ZrSiO4 solid solutions from gels, Ceram. Int. 37 (2011) 3609–3616. [13] R.A. Eppler, Kinetics of formation of an iron-zircon pink color, J. Am. Ceram. Soc. 62 (1979) 47–49. [14] P. Tartaj, T. González-Carreño, C.J. Serna, M. Ocaña, Iron zircon pigments prepared by pyrolysis of aerosols, J. Solid State Chem. 128 (1997) 102–108. [15] R. Udaykiran, S. Vasanthavel, S. Kannan, Coordinative crystallization of ZrSiO4 and α-Fe2O3 composites and their resultant structural, morphological, and mechanical characteristics, Cryst. Growth Des. 15 (2015) 4075–4086. [16] J.A. Badenes, M. Llusar, J.B. Vicent, M.A. Tena, G. Monros, The nature of Pr-ZrSiO4 yellow ceramic pigment, J. Mater. Sci. 37 (2002) 1413–1420. [17] M. Ocaña, A. Caballero, A.R. González-Elipe, P. Tartaj, C.J. Serna, R.I. Merino, The effects of the NaF flux on the oxidation state and localisation of praseodymium in Pr-doped zircon pigments, J. Eur. Ceram. Soc. 19 (1999) 641–648. [18] M. Ocaña, A. Caballero, A.R. González-Elípe, P. Tartaj, C.J. Serna, Valence and localization of praseodymium in Pr-doped zircon, J. Solid State Chem. 139 (1998) 412–415. [19] M. Shoyama, H. Nasu, K. Kamiya, Preparation of rare earth-zircon pigments by the sol-gel method, J. Ceram. Soc. Japan. 106 (1998) 279–284. [20] A. Beltran, S. Bohm, A. Flores-Riveros, J.A. Igualada, G. Monros, J. Andres, V. Luana, A.M. Pendas, Ab initio cluster-in-the -lattice description of vanadiumdoped zircon. Analysis of the impurity centers V4+: ZrSiO4, J. Phys. Chem. 97 (1993) 2555–2559. [21] S. Di Gregorio, M. Greenblatt, J.H. Pifer, M.D. Sturge, An ESR and optical study of V4+ in zircon-type crystals, J. Chem. Phys. 76 (1982) 2931–2937. [22] M. Shoyama, N. Matsumoto, T. Hashimoto, H. Nasu, K. Kamiya, Sol-gel synthesis of zircon-effect of addition of lithium ions, J. Mater. Sci. 33 (1998) 4821–4828. [23] A. García Murillo, F. de J. Carrillo Romo, A.M. Torres Huerta, M.A. Domínguez Crespo, E. Ramírez Meneses, H. Terrones, A. Flores Vela, Microstructural evolution of the system Ni–ZrO2–SiO2 synthesized by the sol–gel process, J. Alloy. Comp. 495 (2010) 574–577. [24] S. Cava, S.M. Tebcherani, S.A. Pianaro, C.A. Paskocimas, E. Longo, J.A. Varela, Síntese e caracterização do sistema ZrO2-SiO2 com adição de cobalto para uso como pigmentos cerâmicos, Cerâmica 51 (2005) 302–307. [25] Q. Zhang, Q. Yang, Y. Sun, H. Wang, Low temperature synthesis of a new yellowish brown ceramic pigment based on FeNbO4@ZrSiO4, Ceram. Int. 44 (2018) 12621–12626. [26] B.H. Toby, A graphical user interface for GSAS, J. Appl. Crystallogr. 34 (2001) 210–213. [27] R.M. Hazen, L.M. Finger, Crystal structure and compressibility of zircon at high pressure, Am. Mineral. 64 (1979) 196–201. [28] R. Norrestam, a-Manganese (III) oxide–A C-type sesquioxide of orthorhombic symmetry, Acta Chem. Scand. 21 (1967) 2871–2884. [29] C.J. Howard, R.J. Hill, B.E. Reichert, Structures of ZrO2 polymorphs at room temperature by high-resolution neutron powder diffraction, Acta Crystallogr. Sect. B Struct. Sci. 44 (1988) 116–120. [30] D.K. Smith, W. Newkirk, The crystal structure of baddeleyite (monoclinic ZrO 2 ) and its relation to the polymorphism of ZrO 2, Acta Crystallogr. 18 (1965) 983–991. [31] P. Dera, J.D. Lazarz, V.B. Prakapenka, M. Barkley, R.T. Downs, New insights into the high-pressure polymorphism of SiO2 cristobalite, Phys. Chem. Miner. 38 (2011) 517–529. [32] S. Vasanthavel, S. Kannan, Phase stabilization of ZrO2 polymorph by combined
11547
Ceramics International 45 (2019) 11539–11548
S. Vasanthavel, et al.
[33]
[34] [35]
[36] [37] [38] [39]
[40] [41]
additions of Ca2+ and PO43- ions through an in situ synthetic approach, J. Am. Ceram. Soc. 97 (2014) 3774–3780. S. Vasanthavel, P. Nandha Kumar, S. Kannan, Quantitative analysis on the influence of SiO2 content on the phase behavior of ZrO2, J. Am. Ceram. Soc. 97 (2014) 635–642. C.M. Phillippi, K.S. Mazdiyasni, Infrared and Raman spectra of zirconia polymorphs, J. Am. Ceram. Soc. 54 (1971) 254–258. R. Udaykiran, S. Vasanthavel, S. Kannan, Coordinative crystallization of ZrSiO4 and α-Fe2O3 composites and their resultant structural, morphological, and mechanical characteristics, Cryst. Growth Des. 15 (2015) 4075–4086. 1372, P. Griffith, W.P.G.T.C. Soc, Raman Studies on Rock-Forming Minerals . Part I . O, (1969), pp. 1372–1377. P. Dawson, M.M. Hargreave, G.R. Wilkinson, The vibrational spectrum of zircon (ZrSiO4), J. Phys. C Solid State Phys. 4 (1971) 240–256. R.W.G. Syme, D.J. Lockwood, H.J. Kerr, Raman spectrum of synthetic zircon (ZrSiO4) and thorite (ThSiO4), J. Phys. C Solid State Phys. 10 (1977) 1335–1348. Z.H. Wang, D.Y. Geng, Y.J. Zhang, Z.D. Zhang, Morphology, structure and magnetic properties of single-crystal Mn3O4nanorods, J. Cryst. Growth 310 (2008) 4148–4151. M. Salavati-Niasari, F. Davar, Synthesis of monodisperse Mn3O4 nanocrystals, Int. J. Nanosci. 08 (2009) 281–283. J.W. Lee, A.S. Hall, J.-D. Kim, T.E. Mallouk, A facile and template-free
[42]
[43] [44] [45]
[46]
[47]
[48]
11548
hydrothermal synthesis of Mn3O4 nanorods on graphene sheets for supercapacitor electrodes with long cycle stability, Chem. Mater. 24 (2012) 1158–1164. A. Moses Ezhil Raj, S.G. Victoria, V.B. Jothy, C. Ravidhas, J. Wollschläger, M. Suendorf, M. Neumann, M. Jayachandran, C. Sanjeeviraja, XRD and XPS characterization of mixed valence Mn3O4 hausmannite thin films prepared by chemical spray pyrolysis technique, Appl. Surf. Sci. 256 (2010) 2920–2926. C. Veytizou, Zircon formation from amorphous silica and tetragonal zirconia: kinetic study and modelling, Solid State Ionics 139 (2001) 315–323. T. Itoh, Formation of polycrystalline zircon (ZrSiO4) from amorphous silica and amorphous zirconia, J. Cryst. Growth 125 (1992) 223–228. S. Vasanthavel, B. Derby, S. Kannan, Stabilization of a t-ZrO 2 polymorph in a glassy SiO2 matrix at elevated temperatures accomplished by ceria additions, Dalton Trans. 46 (2017) 6884–6893. S. Vasanthavel, B. Derby, S. Kannan, Tetragonal to cubic transformation of SiO2 -stabilized ZrO2 polymorph through dysprosium substitutions, Inorg. Chem. 56 (2017) 1273–1281. S. Vasanthavel, S. Awasthi, A. Dhayalan, B. Derby, S. Kannan, Structural, mechanical, imaging and in vitro evaluation of the combined effect of Gd 3+ and Dy 3+ in the ZrO2 –SiO2 binary system, Inorg. Chem. 57 (2018) 4602–4612. A.K. Yadav, V. Ponnilavan, S. Kannan, Crystallization of ZrSiO4 from a SiO2 –ZrO2 binary system: the concomitant effects of heat treatment temperature and TiO2 additions, Cryst. Growth Des. 16 (2016) 5493–5500.