Modified magnetic and optical properties of manganese nanoparticles incorporated europium doped magnesium borotellurite glass

Author’s Accepted Manuscript Modified Magnetic and Optical Properties of Manganese Nanoparticles Incorporated Europium Doped Magnesium Borotellurite Glass Siti Maisarah Aziz, M.R. Sahar, S.K. Ghoshal www.elsevier.com/locate/jmmm

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S0304-8853(16)30695-3 http://dx.doi.org/10.1016/j.jmmm.2016.09.017 MAGMA61798

To appear in: Journal of Magnetism and Magnetic Materials Received date: 17 May 2016 Revised date: 29 August 2016 Accepted date: 2 September 2016 Cite this article as: Siti Maisarah Aziz, M.R. Sahar and S.K. Ghoshal, Modified Magnetic and Optical Properties of Manganese Nanoparticles Incorporated Europium Doped Magnesium Borotellurite Glass, Journal of Magnetism and Magnetic Materials, http://dx.doi.org/10.1016/j.jmmm.2016.09.017 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Modified Magnetic and Optical Properties of Manganese Nanoparticles Incorporated Europium Doped Magnesium Borotellurite Glass Siti Maisarah Aziz1, M. R. Sahar, S.K. Ghoshal Advanced Optical Material Research Group, Department of Physics, Faculty Science, Universiti Teknologi Malaysia, 81310, Skudai, Johor Bahru, Johor, Malaysia. [email protected]

Abstract This paper reports the modified optical and magnetic properties of Europium (Eu3+) ions doped and Manganese nanoparticles (NPs) embedded Magnesium Borotellurite glass synthesized via melt quenching method. The influence of varying Mn NPs concentrations on the magnetic, absorption and emission properties of such glass samples are determined. Stables, transparent and amorphous glasses are obtained. The observed modification of the electronic polarizability is interpreted in terms of the generation of non-bridging oxygen (NBO) and bridging oxygen (BO) in the amorphous network. TEM images manifested the growth of Mn NPs with average diameter 11 ± 1 nm. High-resolution TEM reveals that the lattice spacing of manganese nanoparticles is 0.308 nm at (112) plane. The emission spectra revealed four prominent peaks centred at 587 nm, 610 nm, 651 nm and 700 nm assigned to the transition from 5D0  7FJ ( J = 1, 2, 3, 4) states of Eu3+ ion. A significant drop in the luminescence intensity due to the incorporation of Mn NPs is ascribed to the enhanced energy transfer from the Eu3+ ion to NPs. Prepared glass systems exhibited paramagnetic behaviour.

Keywords: borotellurite; luminescence; magnetic properties; europium; nanoparticles

1.

Introduction In the past few decades, synthesis and characterizations of rare earth ions (REIs)

doped binary and ternary glasses are intensively performed due to their advantages in

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developing efficient photonic devices [1]. Dehelean et al. acknowledged that REIs doped glasses due to their high brightness and improved efficiency are prospective for broad array of technological applications [2]. Modifications in the structural, magnetic and optical properties of REIs doped glasses by embedding various metallic NPs is however a recent research trend. In this view, several attempts are made to improve the optical properties of REIs doped glasses by incorporating various metallic NPs (magnetic and nonmagnetic). Recently, the impact of Ni2+, Fe2+ and Co2+ (transition metal) NPs on the structural, physical and magneto-optic properties of REIs doped binary glasses is examined. Literatures hinted that these types of glasses with tailored properties are greatly potential for the advancement of magneto-optic devices including isolators, switches and sensors [3, 4]. Burger et al. [5] revealed that borotellurite glass system is one of the best hosts because of simple B2O3 and TeO2 structure formation and enhanced stability. Besides, they display low phonon energy, superior thermal stability and high chemical durability [6, 7]. Halimah et al. [8] found TeO2 contents dependent significant improvement in the rigidity of borotellurite glass structure with reduced phonon energy loss. The presence of both B2O3 and TeO2 structural units in the glass leads to a complex speciation within the amorphous network [9]. Borotellurite glass is emerged as a favourable host for accommodating large amount of REIs. Trivalent Eu3+ ion is a well-known activator with simple electronic transitions. The Eu3+ ions possess prominent laser emissions in the orange or red region [10] and narrow band emission [6] with longer lifetime. The incorporation of controlled concentrations of NPs in borotellurite glass provides an opportunity to develop new stable magnetic glasses useful for nonlinear optical sensor, electronics devices and light emitting diodes [11]. High saturation magnetization and magneto-crystalline anisotropy of Mn NPs are useful for [12] creating excellent traps for excited electrons in the glass host. Such electron trapping are advantageous to surmount data 2

corruption in magnetic data storage [13]. Lately, various magnetic NPs embedded glass systems are prepared such as Ni NPs incorporated ZnO-P2O5 glass [14] and Fe3O4 NPs included P2O5-ZnO glass [15]. However, the influence of Mn NPs on the room temperature optical and magnetic properties of europium doped borotellurite glasses is seldom reported. The present paper examines the Mn NPs concentration dependent changes in the physical, optical and magnetic properties of Eu3+ ions doped magnesium borotellurite glasses. 2.

Experimental Procedure Glass systems with nominal composition of (59-x)TeO2-30B2O3-10MgO-1Eu2O3-

(x)Mn3O4, where 0.0 ≤ x ≤ 2.0 mol% are prepared using melt quenching method. Analytical grade powders of TeO2 (Sigma Aldrich, 99.99 %), H3BO3 (Sigma Aldrich 99.99 %), MgO (Sigma Aldrich, 99.99 %), Eu2O3 (Sigma Aldrich, 99.99 %) and Mn3O4 (Alfa Aesar, 99.99 %) are used as glass constituents. A 20 g batch of the mixed constituents is melted in an alumina crucible at 900 °C for 1h in an electrical furnace. Afterward, the molten mixture is poured onto a preheated steel plate for annealing process and kept for 3 h at 300 °C before being cooled down to room temperature. The samples are grinded into powder form for physical, optical and magnetic analysis. Table 1 enlists the nominal composition and the codes of synthesized glass system. The amorphous phases of the synthesized samples are identified using X-ray Diffraction (XRD) measurement (Siemens Diffractometer D5000) in the 2 range of 10o-80o. Absorption spectra in the range of 200-800 nm are recorded using Perkin-Elmer Spectrometer. The thermal parameters in term of glass transition (Tg), crystallization temperature (Tc) and melting point (Tm) are determined using Perkin-Elmer pyris Diamond TG/DTA 7 Series. Absorption coefficient

( ) of each sample is determined using the

relation [16],

3

( )

(1)

where A corresponds to absorbance and t refers to the thickness of the sample. The relation between α (ω) and the photon energy ( (

( ) where

) of incident radiation yields,

)

is indirect optical energy band gap,

(2) is the photon energy and B is a constant

called band tailing parameter. Molar refraction (Rm) is calculated via [17], (3) where n is the glass refractive index and Vm is the molar volume. Meanwhile, the electronic polarizability ( (

) is calculated using [17],

)

(4)

where NA is the Avogadro constant. Following Dimitrov and Sakka [18], n is related to the indirect optical energy band gap, EIopt via, √

(5)

where the value of EIopt is obtained from Mott and Davis equation. The energy dispersive X-ray spectrometer (Swift ED3000 EDX) is used to detect the elemental traces in the glass sample. The presence of Mn NPs is detected using Transmission Electron Microscope (TEM) of Philips CM12 equipped with Docu Version 3.2. The nanoparticles orientation plane in Mn NPs is studied using HRTEM imaging (JEOL 2100F). TEM and HRTEM are operated at an acceleration voltage of 200 kV. Room temperature emission spectra in the wavelength range of 200-900 nm are measure using Jasco FP-8500 Photoluminescence Spectrometer, where a xenon lamp is used as the excitation source. The decay time (half-life) of the excited state is calculated using [19],

4

(6) where A1 and A2 are constants, and τ1 and τ2 are the rapid and slow lifetimes, respectively. For τ1 = τ2, = τ and A1 = A2= A, the intensity is maximum. Eq. (6) is simplified as, (7) such components are modified from the relations of second order exponential equation written as, ( )

(8)

where I is the luminescence intensity when Io of initial luminescence intensity is constant and t is time, which excited at 390 nm with operating power at 20 kW for 8 μs duration. The equation is simplified as below, ( )

(9) The magnetization measurement is carried out using Lake Shore's 7400 Vibrating

Sample Magnetometer (VSM) with a field of 12 kOe. The hysteresis loop is measured (magnetization, M (emug-1) versus external magnetic field, H (Oe)) of magnetic materials without substrate (glass host) for low moment measurement capabilities. Magnetic properties are determined in terms of saturation magnetization, (Ms), remanent magnetization, (Mr) and coercivitiy (Hc). Magnetic susceptibility (

) yields [14], (10)

All the measurements are performed at room temperature. The formation of Mn NPs is attributed to the growth and nucleation process, where the following redox reaction occurred during the melting process[20]: (11) →

(

)

(12)

(

)

(13) 5

The neutral atom (

) first formed the critical nuclei and then nucleated to a NP via

Ostwald ripening and coalescence process. The thermodynamic stability and the free energy minimization are also considered in the formation of NPs. The creation of such NP causes lateral relaxation of the lattice planes which are compressed in the bulk of the glass network and reduced the stored elastic energy. However, the NP also cost additional surface energy. The integrated volume of the NPs increases during the quenching process as some of the Mn atoms move from the wetting layer into the NPs. Although, the transformation from one shape to another complicates the coarsening process but the spherical NPs are most favourable from surface energy cost point of view. Thus, coarsening leads to the evolution toward the lowest-energy configuration of the system consistent with temperature and achieves nearly spherical NPs in equilibrium. The process responsible for coarsening is mainly the Ostwald ripening. Consequently, the free energy of the NP decreases monotonically with increasing NP size. An eventual slowing of the coarsening could be caused by a kinetic barrier to atom attachment to mature the NPs shape and size. Diffusion of Mn from the fluid state into the Mn NP during quenching changes the energetically favourable shape of a given size NPs.

3.

Results and discussions The obtained glasses are stable and visually transparent. They are non-hygroscopic

even after being exposed in air for several days. Fig. 1 shows the typical XRD pattern of the prepared glasses. Absence of any sharp peak in the XRD patterns verified samples amorphous nature. A broad hunch around 25- 35º which aroused from the diffuse scattering clearly indicated the presence of short range atomic arrangement in the material [21]. All the samples showed a similar XRD pattern. Thus, XRD pattern of three samples are provided. 6

The glass stability is verified using DTA analysis (Fig. 2) and the Hruby parameters are calculated. Sample S3 revealed the maximum thermal stability around 124 ºC. According to the literature a glass system is considered as stable when the thermal ability (∆S = Tc-Tg) is greater than 100 °C [22].

Fig. 3(a) displays the TEM images of sample S5. The presence of non-spherical Mn NPs having different sizes and shapes are clearly evidenced as black spots in the glass matrix. Furthermore, the size distribution of Mn NPs is found to be Gaussian (Fig.3 (b)) with average diameter is 11 ± 1 nm. Some Mn NPs are agglomerated due to the high attraction force between the particles [23, 24]. Mn NPs are obtained from Mn3O4 through redox reaction. The occurrence of Mn NPs is verified using the HRTEM analysis as shown in Fig.3 (c). The HRTEM is equipped with Fast Fourier Transform (FFT) software and interfaced with Digital Micrograph 3.3.1 (Gatan Ltd.). A d-spacing of 0.308 nm is measured as displayed in Fig.3 (c), which is comparable to the lattice parameter of pure Mn (d112) = 0.308 nm (JCPDS No. 24-0734) [25]. The existence of Mn NPs in the glass system is also clearly evidenced in the FFT images (Fig.3 (d)). Fig. 4 illustrates the EDX spectra of S5 glass sample revealing the presence of various elements such as Te, B, Mg, Eu, and Mn. A very weak peak of Mn is also observed. Table 2 enlists the calculated and actual percentages of all elements present in the glass sample [16].

Fig. 5 shows the typical optical absorption spectra of sample S1, where the appearance of sharp absorption edge characterized of glassy state. Table 3 enlists the values of cut-off wavelength (λo), optical energy band gap (EIopt), refractive index (n), molar refraction (RM) and electronic polarizability (αe). Cut-off wavelengths are the maximum wavelength (minimum frequency) at which absorption almost complete before the energy is 7

being used to excite electron from the valence band to the conduction band. Thus, the optical energy band initiation can be justified, where Eg can be clarified as the minimum required energy for electron to cross the band gap. The cut-off wavelength is found to shift to the higher wavelength with the increase of Mn NPs concentration. This originated due to the existence of high polarity of Mn NPs that breaks the regular structure of borate and tellurite structural units. Consequently, more non-bridging oxygens (NBO) are formed [9], which carried a partial negative charge to loosely bound to the network. This indicates that a small energy is required to interact with such electrons which shifted the absorption band edge toward higher wavelength and finally diminished the optical energy band gap [17]. Thus, the atomic arrangement in the glass matrix became more randomized. Meanwhile, the value of EIopt is decreased and n is increased with the increase of Mn NPs concentration [26]. However, a reverse trend is occurred beyond a certain concentration of Mn NPs. Fig. 6 depicts the Mn NPs concentration dependent variation in EIopt and n. The refractive indices for the prepared glass samples are increased with the increasing Mn NPs concentration (up to 1 mol%) and then are decrease beyond this value. This observations are attributed to the creation of more NBO inside the glass matrix because the electrons around NBO are weakly bound to the oxygen [21]. The electron cloud reduced the velocity of light through the glass system and responsible for refractive index enhancement. The NBO revealed higher tendency to be polarized as compare to BO, thus increased the electronic polarizability [26]. The observed reduction in both the refractive index and the electronic polarizability beyond 1.0 mol% of Mn NPs are ascribed to the increase of Mn NPs field strength (26.29 Å-2) at the expense of TeO2 one (9.18Å-2). The occupation of Mn NPs in glass network allowed generating more BO. The values of refractive index and electronic polarizability are outlined in Table 3. 8

Fig. 7 illustrates the room temperature emission spectra of all samples under 390 nm excitations. The PL spectra exhibited four significant peaks centred at 587 nm (orange), 610 nm (orange), 651 nm (red), and 700 nm (red), which are assigned to the transition from 5D0

 7FJ ( J = 1, 2, 3, 4) states of Eu3+ ion [27, 28]. The peak for 5D0  7F1 transition is allocated to the magnetic dipole, which scarcely changed the crystal field strength around the Eu3+ ions [28]. Besides, the transition of 5D0  7F2 belonged to a forced electric dipole transition and its intensity appeared very sensitive to the symmetrical site of the Eu3+ ions [26]. The quenching and enhancement factor for each transition is calculated and summarized in Table 4. It is found that the emission intensity for the transition of 5D0  7F2 is much stronger than 5D0  7F1. As the concentration of Mn NPs ions is increased, the intensity of the emission bands are decreased. This decrease in the intensity is ascribed to the energy transfer from Eu3+ ions to the NPs [29]. Further increase of Mn NPs concentration (up to 1.0 mol %) enhanced the emission intensity. This is attributed to the increase in oxygen vacancies created by the Mn NPs and the appearance of NPs surface plasmon resonance (SPR) mediated large local electromagnetic field in the vicinity of Eu3+ ions [30]. Furthermore, the quenching in the PL intensity beyond 1 mol% of Mn NPs is ascribed to the structural modification of the glass network [19]. The energy transfer mechanism is illustrated using partial energy level diagram of Eu3+ ion which appeared in the proximity of Mn NPs (Fig. 8). At the beginning, the electrons are excited from the ground state 7F0 to the upper state 5L2 by ground state absorption (GSA). Then, the electrons are dropped to the metastable level, 5D0 level before it back to the lower state. However, some Eu3+ ions are found to be non-radiatively (NR) relaxed to 5D2, 5D1 and 5D0 levels. These emissions disappeared in luminescence spectra due to energy loss in the form of heat by non-radiative decay process. Finally from 5D0 level, electrons are directly dropped to the 7F1, 7F2, 7F3 and 7F4 9

transition levels. The first wavelength is assigned as orange emission located at 587 nm. The other transitions corresponded to the red emission located 610 nm, 651 nm and 670 nm. Tables 5 and 6 summarizes the calculated full width at half maximum (FWHM) and the quality factor (Q) involving the luminescence spectra.

Fig. 9 shows the Mn NPs concentration dependent Q value, which is an important predictor of stimulated emission for laser active medium [31]. The Q values are increased with the increase of Mn NPs contents. The presence of Mn NPs significantly reduced the nonradiative energy loss by providing strong SPR mediated effects. The higher value of Q indicated more intense laser transitions [32].

Fig. 10 displays the PL intensity decay of 5D0  7F1 transition for sample S3. Table 7 enlists the half-lifetime (τ) of corresponding decay. All decay curves are well fitted to the second order exponential. The calculated value of τ is ranged between 1.44108-1.44267 μs, which is slightly increased with the increase of Mn NPs concentration up to 1.0 mol % and decreased thereafter. Thus, the observed sensitiveness of τ on Mn NPs concentration [14] are consistent with the report of Wang et al. [33], wherein the exchange interaction of the spin selection rule acted as the main contributor to the decay half-life. The occurrence of long half-life is attributed to the magnetic dipole–dipole interaction of NPs [34]. The presence of Mn NPs greatly enhanced the decay rate due to the energy transfer from NPs to Eu3+. However, beyond 1.0 mol %, the reduction in τ values is majorly ascribed to the reverse energy transfer (from Eu3+ to NPs).

Fig. 11 (a) represents the hysteresis loop of the glass system (magnetization versus external magnetic field), where Ms is taken as the maximum value of the loop (indicated by 10

the dotted line) in the Fig.11 (b). The hysteresis loops exhibited strong paramagnetic behaviour with increasing concentration of Mn NPs [35]. Room temperature magnetic properties are measured using VSM under an applied magnetic field of 12 kOe. Table 8 enlists the calculated values of saturation magnetization (Ms), remanent magnetization (Mr), coercivity (Hc), squareness (Mr/Ms) and magnetic susceptibility (χm). From the Fig.11, a plot of Ms and Mr against the concentration of Mn NPs can be made and the results shown in Fig.12.

Fig.12 displays an increasing trend of both Ms and Mr with increasing concentration of Mn NPs. This clearly indicates that the present glass system can serve as good paramagnetic material useful for magneto-optic devices. Zhang et al. [36] acknowledged that increase of Ms is not only decided by the NPs local field environment but also by the changes of their electron spins. Moreover, the occurrence of highest Mr for the sample with 1 mol% of Mn NPs reflects the strongest magnetic properties.

Fig. 13 illustrates the Mn NPs contents dependent magnetic susceptibility [37] of the synthesized glasses, which is significantly increased with the increase of Mn NPs concentration. The measured susceptibility from the hysteresis loop is in the range of to 4.12 to 11.09×10-6 which indicates a paramagnetic behaviour. This is in good agreement with those reported by Azmi et al. [14]. Borotellurite glass system being diamagnetic possesses zero net magnetic moment. However, the introduction of Mn NPs within the glass matrix altered the magnetic properties of the glass system. It is worth noting that pure Mn3O4 NPs containing two different atoms (Mn and O) occupy different lattice positions. These two atoms having equal magnetic moment (magnitude) but opposite in direction cancels each other to produce net zero magnetic moment. However, inside the glass matrix due to the 11

appearance of different magnitudes of these magnetic moments they do not cancel out thus results in a net spontaneous magnetic moment. When such glass system containing magnetic NPs is placed in a magnetic field, they reveal paramagnetic behaviour [38]. This observation can be attributed to the combination of vacancies and Mn3+ cation and subsequent creation of the normal spinel structure [39]. Consequently, the Hausmannite of Mn3O4 (the Mnɪ centres) exclusively occupies the tetrahedral site and the Mnɪ

ɪ ɪ

centre occupies the

octahedral site. The inherent disorder in the glass favours the randomization of Mn ɪ Mnɪ

ɪ ɪ

ɪ

ɪ

and

centre into both octahedral and tetrahedral sites. The presence of defects in such

amorphous material gives rise to coercivity and reveals magnetic behaviour [40]

Fig. 14 (a) displays the Mn NPs concentration dependent coercivity and squareness of the synthesized glass samples [15]. An increase in the Mn NPs concentration increased the average size of nanocrystallites which in turn enhanced the saturation magnetization. The increase of glass coercivity can be explained in terms of the increase of surface anisotropy that happens in spin-glass-like state [41]. Since the coercivity of a material mainly depends on the saturation magnetization anisotropy, thus by increasing the concentration of Mn NPs it can be enhanced. The highest value of Hc is discerned to be 1424.42 ± 71.22 at 1.0 mol% of Mn NPs (Fig. 14(a)). This value of Hc strongly depends on the anisotropy of saturation magnetization and structural parameters [42]. The observed increase of Hc is due to the presence of high surface anisotropy in the glass and dipole interaction between Mn NPs. The occurrence of large Hc value is attributed to two possibilities including the small size of NPs to form a single magnetic domain and the intrinsic magnetic anisotropy [38].

Fig. 14 (b) displays the variation of Mr/Ms for all glass system as a function of Mn NPs concentration. Squareness is a measure of the hysteresis loop [43], which suggested the 12

dominant role played by the uniaxial magnetocrystalline anisotropy. This reconfirmed the good paramagnetic nature of the synthesized glass system.

4.

Conclusion Europium doped magnesium borotellurite glass systems are synthesized by

incorporating Mn NPs of varying concentration. Highly amorphous and transparent glass samples are obtained. The physical, optical and magnetic properties of these glasses are found to be sensitive to Mn NPs concentration variation. The TEM analysis revealed the nucleation of non-spherical Mn NPs of average size is 11 ± 1 nm. The luminescence intensity revealed enhancement at 1.0 mol% of Mn NPs and quenched thereafter. The europium ions 5

D0 level exhibited exponential luminescence decay. The magnetic measurement confirmed

the presence of Mn NPs in the glass sample, which showed paramagnetic behaviour. The magnetic properties (saturation magnetization, remanent magnetization, coercivity, squareness and susceptibility) of the prepared glass samples are significantly improved due to the embedment of Mn NPs. Acknowledgments The authors gratefully acknowledge the financial support from UTM and Malaysian Ministry of Education through the Vot. 12H42, 05H36, and 4F424.

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W. Widanarto, M. Sahar, S. Ghoshal, R. Arifin, M. Rohani, and M. Effendi, Thermal, structural and magnetic properties of zinc-tellurite glasses containing natural ferrite oxide, Materials Letters, vol. 108, pp. 289-292, 2013. H. El Ghandoor, H. Zidan, M. M. Khalil, and M. Ismail, Synthesis and some physical properties of magnetite (Fe3O4) nanoparticles, Int. J. Electrochem. Sci, vol. 7, pp. 5734-5745, 2012. L. Zhang and Y. Zhang, Fabrication and magnetic properties of Fe3O4 nanowire arrays in different diameters, Journal of Magnetism and Magnetic Materials, vol. 321, pp. L15-L20, 2009. P. Hu, S. Zhang, H. Wang, D. a. Pan, J. Tian, Z. Tang, et al., Heat treatment effects on Fe3O4 nanoparticles structure and magnetic properties prepared by carbothermal reduction, Journal of Alloys and Compounds, vol. 509, pp. 2316-2319, 2011. B. Issa, I. M. Obaidat, B. A. Albiss, and Y. Haik, Magnetic nanoparticles: surface effects and properties related to biomedicine applications, Int J Mol Sci, vol. 14, pp. 21266-305, 2013. A. E. Berkowitz, G. F. Rodriguez, J. I. Hong, K. An, T. Hyeon, N. Agarwal, et al., Monodispersed MnO nanoparticles with epitaxial Mn3O4shells, Journal of Physics D: Applied Physics, vol. 41, p. 134007, 2008. A. Buckelew, J. R. Galan-Mascaros, and K. R. Dunbar, Facile Conversion of the Face-Centered Cubic Prussian-Blue Material K2[Mn2(CN)6] into the Spinel Oxide Mn3O4 at the Solid/Water Interface, Advanced Materials, vol. 14, pp. 1646-1648, 2002. M. Tadić, M. Panjan, D. Marković, I. Milošević, and V. Spasojević, Unusual magnetic properties of NiO nanoparticles embedded in a silica matrix, Journal of Alloys and Compounds, vol. 509, pp. 7134-7138, 2011. X. Liang, H. Shi, X. Jia, Y. Yang, and X. Liu, Dispersibility, Shape and Magnetic Properties of Nano-Fe3O4 Particles, Materials Sciences and Applications, vol. 02, pp. 1644-1653, 2011. R. Bhowmik, V. Vasanthi, and A. Poddar, Alloying of Fe3O4 and Co3O4 to develop Co3x Fe3(1−x)O4 ferrite with high magnetic squareness, tunable ferromagnetic parameters, and exchange bias, Journal of Alloys and Compounds, vol. 578, pp. 585594, 2013.

FIGURE CAPTIONS Fig.1. XRD pattern of S1, S2 and S3 glass system.

16

Fig.2. Typical DTA curves of synthesized borotellurite glass with 1 mol% of Mn NPs. Exo: Exothermic (upward) and Endo: Endothermic (downward). Fig.3. (a) TEM images of S5 sample displaying the distribution of non-spherical Mn NPs and (b) corresponding size distribution (c) d-spacing of Mn NPs along (112) lattice plane and (d) FFT image of Mn NPs

Fig.4. EDX spectra of S5 sample.

Fig.5. Typical absorption spectra of sample S1 showing the cut-off wavelength Fig.6. Mn NPs concentration (mol%) dependent variation of EIopt and n. Fig.7. Mn NPs concentration dependent luminescence spectra of synthesized glasses. Fig.8. Partial energy level of Eu3+ under 390 nm excitations for down-conversion emission (ET-E: Energy Transfer Enhancement and ET-Q: Energy Transfer Quenching).

Fig.9. Mn NPs contents dependent Q for various PL peaks. Fig.10. Decay analysis of S3 for 5D0-7F1 transition in PL intensity curve.

Fig.11. (a) The magnetization against external magnetic field of prepared glass samples (b) The value of Ms and Mr for sample S4 as obtained from the graph of M against H. The inset shows the samples coercivity (Hc). Fig.12. Mn NPs concentration dependent Ms and Mr Fig.13. Variation of χm as a function of Mn NPs concentration. Fig.14. Mn NPs concentration dependent (a) coercivity (Hc), and (b) squareness (Mr/Ms) for all glass samples.

17

Table 1Nominal composition of prepared glass system

Sample

Table 2 and

Nominal composition (mol %) B2O3

TeO2

MgO

Eu2O3

Mn3O4

S1

30.0

59.0

10.0

1.0

0.0

S2

30.0

58.5

10.0

1.0

0.5

S3

30.0

58.0

10.0

1.0

1.0

S4

30.0

57.5

10.0

1.0

1.5

S5

30.0

57.0

10.0

1.0

2.0

Nominal actual

composition of sample S5

TeO2

B2O3

MgO

Eu2O3

Mn3O4

Nominal (mol %)

58.0

30.0

10.0

1.0

2.0

Actual

24.6

70.3

3.3

1.5

0.2

(mol %)

Table 3 Mn NPs concentration dependent optical properties of the prepared glass system displaying the respective errors in the measurement Mn3O4

λo

Eopt

n

RM (cm3mol-1)

αe (Å3)

(mol %)

(±0.01nm)

( ±0.01eV)

(±0.01)

(±0.01)

(±0.01)

S1

0.0

4.40

3.27

2.32

15.44

6.12

S2

0.5

4.42

3.03

2.38

15.81

6.27

S3

1.0

4.44

2.61

2.50

16.52

6.55

S4

1.5

4.37

2.87

2.43

15.97

6.33

S5

2.0

4.35

2.91

2.41

15.81

6.27

Sample

Table 4 Mn NPs concentration dependent ratio of integrated emission intensity

Sample

Mn3O4 (mol %)

Iint 18

S1

0.0

1: 1:1:1

S2

0.5

0.076 : 0.076 : 0.075 : 0.074

S3

1.0

2.30 : 2.11: 3.15 : 2.59

S4

1.5

0.85 : 0.87 : 0.92 : 0.96

S5

2.0

0.32 : 0.18 : 0.48 : 0.19

Table 5 FHWM (nm) for all emission peaks of prepared glasses

Sample

Mn3O4

FWHM for transition of 5

(mol %)

D0 → 7F1

5

D0 → 7F2

5

D0 → 7F3

5

D0 → 7F4

S1

0.0

11.87

11.07

7.51

12.10

S2

0.5

12.86

10.92

7.05

12.53

S3

1.0

10.90

10.64

5.40

11.92

S4

1.5

10.97

11.19

6.98

12.15

S5

2.0

11.25

11.25

6.32

12.51

Table 6 Quality factors of all emission peak of prepared glasses

Sample

Mn3O4 (mol %)

Quality factor 5

D0 → 7F1

5

D0 → 7F2

5

D0 → 7F3

5

D0 → 7F4

S1

0.0

49.78

55.46

86.68

57.55

S2

0.5

45.95

56.22

92.34

56.30

S3

1.0

54.22

57.66

120.26

58.82

S4

1.5

53.87

54.83

96.20

57.66

S5

2.0

52.53

54.57

110.55

60.21

Table 7 Mn NPs concentration dependent τ value of 5D0 → 7F1 transitions 19

Mn3O4

Transition 5D0 → 7F1

(mol %)

λemission (nm)

S1

0.0

590

1.44108

S2

0.5

590

1.44108

S3

1.0

591

1.44267

S4

1.5

592

1.44253

S5

2.0

592

1.44253

Sample

τ (μs)

Table 8 Values of Ms, Mr, Hc, Mr/Ms and χm of prepared borotellurite glasses

Sample Mn3O4

Magnetic parameters

(mol

Ms (emug-

Mr (emug-1)

%)

1

10-3

)

Hc (Oe)

10-2 S1

0.0

4.95±0.24

0.674 ±0.03

128.25

Mr/Ms (emug-

χm (emuOe-

1

)

1 -1

10-2

 10-6

1.36±0.06

4.12±0.21

g )

±6.41 S2

0.5

5.45±0.27

0.971±0.04

162.01 ±8.10

S3

1.0

8.11±0.40

4.064±0.20

1424.42

4.54±0.23 1.78±0.08 5.01±0.25

6.76±0.34

±71.22 S4

1.5

8.49±0.42

2.303±0.11

81.61 ±4.08

7.08±0.35 2.71±0.13

S5

2.0

13.31±0.66

2.139±0.10

4.19 ±0.20

1.61 ±0.08

11.09±0.55

Graphical Abstract

20

Highlight    

The europium doped magnesium borotellurite glasses embedded Mn NPs prepared using the conventional melt-quenching method. The TEM result reveals the size of Mn NPs while its planar spacing has been determined by HRTEM. The luminescence properties of TeO2-B2O3-MgO-Eu2O3-Mn3O4 glasses have been investigated as effect of Mn NPs content. The magnetization measurement of glass sample is carried out using vibrating sample magnetometer (VSM)

LIST OF FIGURE FIGURE 1

LIST OF FIGURE

Intensity (a.u.)

FIGURE 1

S1 S2 S3

10

20

30

40 50 60 2 (degree)

70

80

90

21

FIGURE 2

Heat flow (mW/mg)

Exo.

20

T g

10 0

T c

S3

T m

-10 -20 -30 -40

-50 Endo.

0

200 400 600 800 1000 Temperature (C)

22

FIGURE 3

Abundance (%)

(b)

Gaussion fit Average diameter ~ 11 nm

15

10

5

0 3

6

9 12 15 Particle size (nm)

18

21

23

FIGURE 4

24

FIGURE 5

Absorbance (a.u.)

S1

400

500 600 Wavelength (nm)

700

25

FIGURE 6

EI opt n

2.50 2.45

3.0

I

2.40

n

Eopt(eV)

3.2

2.8 2.35 2.6

2.30 0.0

0.5 1.0 1.5 2.0 Mn NPs concentration (mol%)

26

FIGURE7

Intensity (a.u.)

5 D 7 F 2 0 610 nm

587 nm 5 D 7 F 1 0

550

S1 S2 S3 S4 S5

700 nm 651 nm 5 D 7 F 4 7F 0 5D 0 3

600 650 700 Wavelength (nm)

750

27

FIGURE 8

28

FIGURE 9

125 S1 S2 S3 S4 S5

Q

100

5D

7 0  F3

75 5D  7F 0 1

50

5D  7F 0 2

1

2 3 Transition

5D  7F 0 4

4

29

Normalized intensity (a.u.)

FIGURE 10

1.0 0.8 0.6 0.4 0.2 0.0 0

2

4

6 8 Time (s)

10

12

30

FIGURE 11

S1 S2 S3 S4 S5

(a) -1

M (emug )

0.18 0.09 0.00 -0.09

-0.18 -15000-10000-5000 0 5000 10000 15000 H (Oe) S4

0.09 0.00

M s M r 0.04

-0.09

M (emug-1)

-1

M (emug )

0.18

0.00

Hc

-0.04 -2000 0 2000 H (Oe) -0.18 -15000-10000 -5000 0 5000 10000 15000 H (Oe)

31

32

FIGURE 12

12

4.5 -1

Mr

Mr (10 emug )

3.0

-3

-2

-1

Ms (10 emug )

Ms

9 1.5 6 0.0 0.0

0.5 1.0 1.5 2.0 Mn NPs concentration (mol%)

33

FIGURE 13

10 8

-6

-1 -1

m (10 emuOe g )

12

6 4 0.0 0.5 1.0 1.5 2.0 Mn NPs concentration (mol%)

34

FIGURE 14 (a)

1500 (a)

Hc (Oe)

1000

500

0 0.0 0.5 1.0 1.5 2.0 Mn NPs concentration (mol%)

35

FIGURE 14(b)

4.5

-2

-1

Mr/Ms (10 emug )

(b)

3.0

1.5 0.0 0.5 1.0 1.5 2.0 Mn NPs concentration (mol%)

36

Intensity (a.u.)

S1 S2 S3

10

20

30

40 50 60 2 (degree)

70

80

90

37

FIGURE 2

Heat flow (mW/mg)

Exo.

20

T g

10 0

T c

S3

T m

-10 -20 -30 -40

-50 Endo.

0

200 400 600 800 1000 Temperature (C)

38

FIGURE 3

Abundance (%)

(b)

Gaussion fit Average diameter ~ 11 nm

15

10

5

0 3

6

9 12 15 Particle size (nm)

18

21

39

FIGURE 4

40

FIGURE 5

Absorbance (a.u.)

S1

400

500 600 Wavelength (nm)

700

41

FIGURE 6

EI opt n

2.50 2.45

3.0

I

2.40

n

Eopt(eV)

3.2

2.8 2.35 2.6

2.30 0.0

0.5 1.0 1.5 2.0 Mn NPs concentration (mol%)

42

FIGURE7

Intensity (a.u.)

5 D 7 F 2 0 610 nm

587 nm 5 D 7 F 1 0

550

S1 S2 S3 S4 S5

700 nm 651 nm 5 D 7 F 4 7F 0 5D 0 3

600 650 700 Wavelength (nm)

750

43

FIGURE 8

44

FIGURE 9

125 S1 S2 S3 S4 S5

Q

100

5D

7 0  F3

75 5D  7F 0 1

50

5D  7F 0 2

1

2 3 Transition

5D  7F 0 4

4

45

Normalized intensity (a.u.)

FIGURE 10

1.0 0.8 0.6 0.4 0.2 0.0 0

2

4

6 8 Time (s)

10

12

46

FIGURE 11

S1 S2 S3 S4 S5

(a) -1

M (emug )

0.18 0.09 0.00 -0.09

-0.18 -15000-10000-5000 0 5000 10000 15000 H (Oe) S4

0.09 0.00

M s M r 0.04

-0.09

M (emug-1)

-1

M (emug )

0.18

0.00

Hc

-0.04 -2000 0 2000 H (Oe) -0.18 -15000-10000 -5000 0 5000 10000 15000 H (Oe)

47

48

FIGURE 12

12

4.5 -1

Mr

Mr (10 emug )

3.0

-3

-2

-1

Ms (10 emug )

Ms

9 1.5 6 0.0 0.0

0.5 1.0 1.5 2.0 Mn NPs concentration (mol%)

49

FIGURE 13

10 8

-6

-1 -1

m (10 emuOe g )

12

6 4 0.0 0.5 1.0 1.5 2.0 Mn NPs concentration (mol%)

50

FIGURE 14 (a)

1500 (a)

Hc (Oe)

1000

500

0 0.0 0.5 1.0 1.5 2.0 Mn NPs concentration (mol%)

51

FIGURE 14(b)

4.5

-2

-1

Mr/Ms (10 emug )

(b)

3.0

1.5 0.0 0.5 1.0 1.5 2.0 Mn NPs concentration (mol%)

52

Graphical Abstract (a)

Intensity (a.u.)

5 D 7 F 2 0 610 nm

587 nm 5 D 7 F 1 0

550

S1 S2 S3 S4 S5

700 nm 651 nm 5 D 7 F 4 7F 0 5D 0 3

600 650 700 Wavelength (nm)

750

(b)

(a) -1

M (emug )

0.18 0.09

S1 S2 S3 S4 S5

0.00 -0.09 -0.18 -15000-10000-5000 0 5000 10000 15000 H (Oe)