Influence of NiO on phase transformations and optical properties of ZnO–Al2O3–SiO2 glass-ceramics nucleated by TiO2 and ZrO2. Part I. Influence of NiO on phase transformations of ZnO–Al2O3–SiO2 glass-ceramics nucleated by TiO2 and ZrO2

NOC-16591; No of Pages 10 Journal of Non-Crystalline Solids xxx (2013) xxx–xxx

Contents lists available at SciVerse ScienceDirect

Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/ locate/ jnoncrysol

Influence of NiO on phase transformations and optical properties of ZnO–Al2O3–SiO2 glass-ceramics nucleated by TiO2 and ZrO2. Part I. Influence of NiO on phase transformations of ZnO–Al2O3–SiO2 glass-ceramics nucleated by TiO2 and ZrO2 I.P. Alekseeva a, O.S. Dymshits a,⁎, V.V. Golubkov b, P.A. Loiko c, M.Ya. Tsenter a, K.V. Yumashev c,1, S.S. Zapalova a, A.A. Zhilin a a b c

NITIOM S.I. Vavilov State Optical Institute, 36/1 Babushkin St., Saint-Petersburg 192171, Russia I.V. Grebenschikov Institute of Silicate Chemistry, Russian Academy of Science, Odoevskogo str., Saint-Petersburg 199155, Russia Center for Optical Materials and Technologies, Belarusian National Technical University, 65/17 Nezavisimosti Ave., Rm.#210, Minsk 220013, Belarus

a r t i c l e

i n f o

Article history: Received 25 April 2013 Received in revised form 25 May 2013 Available online xxxx Keywords: Transparent glass-ceramics; Gahnite nanocrystals; Small angle X-ray scattering; Raman spectroscopy; Absorption

a b s t r a c t The influence of NiO addition (from 0.1 up to 3 mol%) on structure and phase transformations of zinc aluminosilicate glasses nucleated by a mixture of TiO2 and ZrO2 has been studied using small angle X-ray scattering (SAXS), X-ray diffraction (XRD) analysis, Raman scattering and optical absorption spectroscopy. All parent glasses were X-ray amorphous and according to SAXS data inhomogeneous. Though SAXS intensity increased with increasing the NiO content in parent glasses, the distance between the inhomogeneous regions was independent of the NiO content implying that NiO does not play a role of additional nucleating agent. The processes of phase transformations were different for glasses doped with 0–0.1 and 1–3 mol% NiO. In glasses containing 0–0.1 mol% NiO, ZrTiO4 and Ni,Ti-doped gahnite crystals precipitated simultaneously starting from heat-treatment at above 730 °C; traces of ZrO2 tetragonal crystals were found in glass-ceramics prepared at 1000–1200 °C. In glasses doped with 1–3 mol% NiO, metastable nickel titanate-zirconate crystals with fluorite-type structure and size of 4–5 nm appeared during heat-treatments in the temperature range of 730–800 °C, the fraction of this phase increased with the increase of the NiO content in the parent glass. Nickel titanate-zirconate crystals with fluorite structure decomposed during annealing at above 800 °C. Ni, Ti-doped gahnite crystals precipitated starting from heat-treatment at 800 °C; ZrO2 tetragonal crystals were formed at 900–1200 °C. © 2013 Elsevier B.V. All rights reserved.

1. Introduction Previously we studied the influence of doping the parent glasses with relatively small amounts of alkali and divalent metal oxides on the kinetics of phase separation and phase assemblage of glass-ceramics of lithium-aluminosilicate (LAS) [1–4], magnesium-aluminosilicate (MAS) [5–7] and zinc-aluminosilicate (ZAS) [8] systems by optical and Raman spectroscopy, X-ray diffraction analysis and small-angle X-ray scattering. Introduced in tiny quantities, these additives affect the kinetics of phase separation by means of enlarging or shortening temperature ranges of existence of various metastable phases; while added in larger concentrations the additives often develop their own crystalline phases. Ni2+-doped crystals exhibit broad-band emission in the infrared spectral range with a high life time and quantum efficiency, which is due to the 3T2 (3F) → 3A2 (3F) transition of Ni2+ ions in octahedral ⁎ Corresponding author. Tel.: +7 8125601911; fax: +7 8125601022. E-mail addresses: [email protected], [email protected] (O.S. Dymshits). 1 Tel.: +7 812 5601911.

coordination [9–14 and references therein]. Recently transparent NiO-doped glass-ceramics containing various crystals with spinel structure were successfully elaborated and shown to have efficient broadband emission in the near-infrared region [15–22]. Moreover, broadband optical amplification and tunable near-infrared luminescence in Ni-doped glass-ceramics were demonstrated [23–25]. The emitting centers are Ni2+ ions located in spinel nanocrystals in octahedral coordination sites. The structural formula of spinel can be described as IV[A1-δBδ]VI[B2-δAδ]O4, where IV[] and VI[] represent the tetrahedral and octahedral sites, respectively; the inversion parameter δ reflects the degree of disorder. There are two ordered configurations of cations in spinels; the normal spinel with δ = 0; and the inverse spinel with δ = 1. Spinels can demonstrate some degree of cation disorder. The distribution of Ni2+ ions between the octahedral and tetrahedral sites in spinels is the function of spinel composition, NiO concentration and conditions of preparation (temperature, time, pressure, etc.) [26]. The detailed knowledge of regularities of phase separation and crystallization of Ni2+-doped glasses, distribution of Ni2+ ions between different phases in glass-ceramics and between

0022-3093/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jnoncrysol.2013.05.038

Please cite this article as: I.P. Alekseeva, et al., Influence of NiO on phase transformations and optical properties of ZnO–Al2O3–SiO2 glass-ceramics nucleated by TiO2 and..., J. Non-Cryst. Solids (2013), http://dx.doi.org/10.1016/j.jnoncrysol.2013.05.038

2

I.P. Alekseeva et al. / Journal of Non-Crystalline Solids xxx (2013) xxx–xxx

octahedral and tetrahedral sites in spinel crystals will allow controlling the luminescence efficiency of the material in the near IR spectral range. The aim of the present study is to follow the evolution of structure of ZAS glass-ceramics doped with nickel oxide (0–3.0 mol%), containing gahnite crystals with spinel structure and prepared at different heat-treatment schedules, and to connect it with their optical properties using small angle X-ray scattering (SAXS), X-ray diffraction analysis (XRD), Raman and optical spectroscopy.

The position of the maximum Qm on the Q dependence of QI(Q) corresponds to the inverse radius of the scattering regions while the shift of its position manifests the radius change. In the case of monomodal system of scattering particles, in condition of Guineir equation validity, there is a dependence between the radius of scattering regions, R, and the Qm value corresponding to maximum on the curve of QI(Q) vs. Q [28]: R¼

2. Experimental The ZAS glass with the composition 25ZnO, 25Al2O3, 50SiO2 (mol%) was nucleated by a mixture of 5TiO2 and 5ZrO2 and doped with 0.1–3.0 mol% NiO introduced above total 100%. The glass of the same composition without NiO and the glass 25ZnO, 25Al2O3, 50SiO2 (mol%) were also prepared. Glasses were melted at 1580 °C for 3 h with stirring, poured onto a metal plate, annealed at 660 °C and heattreated at temperatures from 730 °C to 1200 °C for 6–48 h. For identification of Raman bands that were not previously observed in spectra of undoped glass-ceramics of ZAS system [27] we prepared model compounds which correspond to various crystalline phases with spinel structure that can crystallize in glasses. They are gahnite, ZnAl2O4, in various proportions with Zn2TiO4, ZnNiTiO4 and Ni2TiO4. All the model polycrystalline compounds were synthesized by sintering from mixtures of oxides ZnO, Al2O3, NiO and TiO2 in the temperature range from 1220 to 1450 °C for 24–48 h. Polished samples with thickness of about 0.2 mm were investigated using small angle X-ray scattering (SAXS). The measurements were carried out with a home-made instrument in a range from 6 to 450 arc min which corresponds to scattering vector range (Q) from 8 · 10−3 Å−1 to 0.5 Å−1 where Q = (4π/λ)sin(φ/2), λ is the X-ray wavelength and φ is a scattering angle. CuКα radiation with a Ni filter and an “infinitely” high primary beam was exploited. For a monomodal system of scattering regions angular dependence of the scattered intensity at small angles is
 2 2 2 IðQ Þ ≅ Nn ехр −Q Rg =3 at QRg ≪1 ð1Þ and asymptotic dependence at large angles is 2

4

IðQ Þ ≅ 2πðρ1 −ρ2 Þ S=Q at QRg ≫1

ð2Þ

where N is the number of scattering regions, n is the number of scattering electrons in the scattering region, Rg is a gyration radius, ρ1 and ρ2 are the mean electron densities of the inhomogeneous regions and the surrounding matrix, and S is a surface of the interface of phases. In the case of spherical scattering regions of radius R, R2 = 5/3 R2g. In a general case of a multiphase system, the mean square of the electron density difference, |(Δρ)2|, characterizes the inhomogeneity of the whole structure of the material. For the two-phase materials,    2 2 ðΔρÞ  ¼ ðρ1 −ρ2 Þ w1 w2

ð3Þ

where w1 and w2 are the respective volumes of the inhomogeneous regions and of the surrounding matrix. SAXS curves of phase-separated glasses often exhibit maximum. One of the reasons for its appearance is the regularity in a distribution of scattering regions in the glass volume. Then Q corresponding to the maximum on the curve (Qm) and the distance between centers of regularly distributed particle (L) are connected as 3

L ≅ ð3:3  3:5Þ10 Q m

−1

ð4Þ

where L is a distance between centers of regularly distributed particles (in Å) and Qm is the scattering vector corresponding to the maximum on the scattering curve.

rffiffiffi 5 −1 Q : 2 m

ð5Þ

If there are several phases with mean sizes that differ substantially (two times or even more), the curve of the angular dependence of QI(Q) can exhibit several maximums; intensity of scattering by large and small regions of inhomogeneity can be separated and the mean size of each type of regions of inhomogeneity and SAXS intensity by each fraction can be obtained. X-ray diffraction (XRD) patterns of powdered samples were measured using Shimadzu XRD-6000 diffractometer, CuKα radiation with a Ni filter. The mean crystal sizes were estimated from broadening of X-ray peaks according to Scherrer's equation: D ¼ Kλ=Δð2θÞ cos θ

ð6Þ

where K is a constant assumed to be 1 [29], λ is a wavelength of X-ray radiation, θ is a diffraction angle, and Δ(2θ) is a width of peak at half of its maximum. The unit cell parameter a was estimated from the position of the (440) plane of the gahnite crystal. Relative amounts of gahnite were estimated by measuring integrated intensity of the main diffraction peak of gahnite around 2θ = 36.8°, which corresponds to the reflection from the (311) plane [30]. Raman spectra were recorded in backscattering geometry with the use of Renishaw 1000 Micro-Raman spectrometer equipped with TE cooled CCD camera. The spectra were excited by Ar+ CW laser line of 514 nm. Each sample was carefully positioned to the focus of the exciting laser beam, which resulted in a good reproducibility of spectra and allowed to compare intensities of similar Raman bands in spectra of different samples. Absorption spectra of the samples in the wavelength ranging 340–3100 nm were recorded on 0.5–1 mm thick polished samples by means of a Varian Cary-5000 spectrophotometer. Luminescence was excited by cw radiation of 960 nm InGaAs laser diode. Luminescence was collected in the direction perpendicular to the direction of pump light propagation by means of a wide-aperture lens. The spectrum was recorded by a lock-in amplifier and monochromator with a photodetector attached to its output slit. 3. Results 3.1. Parent glasses All parent glasses doped with NiO were transparent and browncolored. According to XRD data, they were amorphous. 3.1.1. SAXS findings The dependence of SAXS intensity on Q for parent glasses doped with 0.1 and 2.0 mol% NiO is shown in Fig. 1a. In the range of small Q values, scattering by the 2Ni:ZAS glass is much higher than that by the 0.1Ni:ZAS glass; at larger Q values the curves coincide (Fig. 1b. Both curves have a maximum at Q = 0.011 Å−1 (φ = 9.5′). The appearance of this maximum reflects the regularity in a distribution of scattering regions in the glass volume. A distance between centers of regularly distributed large inhomogeneous regions calculated using Eq. (4) is 300 ± 10 Å independently of the NiO content. In Fig. 1b, wherein the SAXS intensity by the 2Ni:ZAS parent glass is plotted in a log–log scale, there is a region with the scattering slope

Please cite this article as: I.P. Alekseeva, et al., Influence of NiO on phase transformations and optical properties of ZnO–Al2O3–SiO2 glass-ceramics nucleated by TiO2 and..., J. Non-Cryst. Solids (2013), http://dx.doi.org/10.1016/j.jnoncrysol.2013.05.038

I.P. Alekseeva et al. / Journal of Non-Crystalline Solids xxx (2013) xxx–xxx

a

2NiO

1800

2NiO

140

1600

120

1400

QI(Q) (arb. units)

100 80 60

0.1NiO

1200 1000

40

600

0.1NiO

200 0

0 0,00

0,01

0,02

0,03

Q

0,04

0,0

0,05

0,1

0,2

0,3

0,4

0,5

Q (A-1)

(A-1)

b

2NiO 100

Fig. 2. Dependences of QI(Q) on Q for parent glasses. The dashed line marks the position of the maximum on QI(Q) curves.

and mean distances between their centers are similar for both glasses, the reason of this increase is an increase of the NiO content in these regions. The |(Δρ)2| for small-size inhomogeneous regions is similar for both glasses.

0.1NiO

1

0,1

0,01 0,01

0,1

Q (A-1) Fig. 1. (a) Dependences of I(Q) on Q for parent glasses. The dashed line marks the position of the maximum on I(Q) curves. (b) Dependences of scattering intensity I(Q) on Q plotted on a log–log scale. The dashed line indicates the scattering slope of 1/3.

of 1/3 at Q = 0.035–0.053 (φ = 30–60′) due to interface effects in scattering by large particles. The bump after this linear portion of the curve indicates the presence of smaller particles. The radii of large and small inhomogeneous regions calculated from the positions of maximums of the QI(Q) dependence (Fig. 2) using Eq. (5) are 110 Å and ~12–15 Å, respectively. The sharp peak of the QΙ(Q) dependence on Q proves the narrow size distribution of large inhomogeneous regions in the 2Ni:ZAS parent glass. The angular dependence of SAXS intensity by the 0.1Ni:ZAS parent glass plotted in a log–log scale (Fig. 1b) also confirms a bimodality of structure, i.e., formation of large and small size inhomogeneous regions. The radius of the larger particles is 110 Å, i.e. the same as in the 2Ni:ZAS glass, but the intensity of SAXS scattering is less (Fig. 2). The size distribution of large inhomogeneous regions is much broader than in the 2Ni:ZAS parent glass: there is a broad maximum on the Q dependence of QΙ(Q) (Fig. 2) and a lack of the linear portion of the curve plotted in a log–log scale (Fig. 1b). At Q values larger than 0.06–0.07 Å, the angular dependence of SAXS intensity by the 2Ni:ZAS and 0.1Ni:ZAS parent glasses coincides, which means that the fine structure of these samples determined by the small size inhomogeneous regions is similar for both glasses. For the glass doped with 2 mol% NiO, the |(Δρ)2| value for large inhomogeneous regions is about 6 times as large as for glass doped with 0.1 mol% NiO. Considering that sizes of large inhomogeneous regions

3.1.2. Absorption spectra Absorption spectra of glasses doped with 0.1 and 1% NiO are shown in Fig. 3 as an example. The spectrum is comprised of three broad asymmetric absorption bands centered at about 430, 870 and 1690 nm, which is typical for Ni-doped silicate and aluminosilicate glasses and can be assigned to absorption of trigonal bipyramid fivefold and tetrahedral fourfold Ni2+ species [31] with the predominance of [V] Ni2+ species. The detailed interpretation of absorption spectra of parent glasses is presented in Part II of this paper [32]. The dependences of absorption in maximums of absorption bands on NiO content are shown in the inset of Fig. 3. For the selected thicknesses of samples we were able to estimate the applicability of the Beer's law for the whole range of NiO concentrations only for bands with maximums at 870 and 1690 nm. The substantial deviation from the Beer's law is observed for glasses doped with 2 and 3 mol% NiO.

30

absorption coefficient (cm-1)

SAXS intensity (arb. unuts)

800

400

20

10

R = 110 A

Absorption coefficient (cm-1)

SAXS intensity (arb. units)

160

3

25

20

15

30 0.43 μm

25 20 0.87 μm

15

1.69 μm

10 5 0 0

1

2

3

NiO content (mol%)

10

1.0NiO 5

0.1NiO 0 500

1000

1500

2000

2500

wavelength (nm) Fig. 3. Absorption spectra of parent glasses doped with 0.1 and 1.0 mol% NiO. Inset presents dependence of intensity in maximums of the absorption bands at 1.69, 0.87 and 0.43 μm on NiO concentration.

Please cite this article as: I.P. Alekseeva, et al., Influence of NiO on phase transformations and optical properties of ZnO–Al2O3–SiO2 glass-ceramics nucleated by TiO2 and..., J. Non-Cryst. Solids (2013), http://dx.doi.org/10.1016/j.jnoncrysol.2013.05.038

4

I.P. Alekseeva et al. / Journal of Non-Crystalline Solids xxx (2013) xxx–xxx

3.1.3. Raman spectra In Raman spectra of parent glasses there are three main broad bands at ~ 450, 800 and 920 cm−1 (Fig. 4). The band at 920 cm−1 is connected with [TiO4] tetrahedra entered into the silicate network [33] while the bands with lower frequency are characteristic of vibrations of silicate network itself [34]. Considering that vibrations of Ti\O bonds in phase separated glasses also locate in the range of ~ 800 cm−1 [2], we estimated the ratio of intensities in maximums of the bands located at ~ 800 and at ~ 450 cm−1 (I800/I450) in Raman spectra of all studied ZAS glasses and compared them with that for glass of the same composition that does not contain any nucleating agent (Table 1). Intensity of the first band was taken from the lowfrequency slope of the broad band at 920 cm−1 while intensity of the band at ~ 450 cm−1 was taken from the background intensity (Fig. 4). This ratio coincides in the spectra of the three glasses: glass without TiO2 and ZrO2, glass nucleated by TiO2 and ZrO2 with no NiO and glass nucleated by TiO2 and ZrO2 and doped with 0.1% NiO. With increasing the content of nickel oxide this ratio increases and for parent glass doped with 3% NiO more than twice exceeds the ratio obtained for glass doped with 0.1% NiO implying that the addition of NiO promotes phase separation of parent glasses.

Table 1 Relative intensities of Raman bands in spectra of parent glasses. N

Glass designation

I800 cm−1/I450 cm−1

I800 cm−1/I900 cm−1

1 2a 3 4 5 6

Glass Glass Glass Glass Glass Glass

0.34 0.33 0.32 0.39 0.47 0.70

– 0.17 0.17 0.22 0.30 0.30

a

without nucleators doped with 0 mol% NiO doped with 0.1 mol% NiO doped with 1 mol% NiO doped with 2 mol% NiO doped with 3 mol% NiO

0.02 0.02 0.02 0.02 0.02 0.02

a

v ZrO2 o Ni,Ti:ZnAl2O4

Intensity (arb.units)

o o 800 C/6h+ o 1100 C/6h o 800oC/6h+ 950 C/6h o

780 C/6h

v o

v o

o o vv

+

o

o o

v v

o o+++ o

+ +

o

o

++

o o

+o+ +o

10

20

30

40

50

60

70

80

2θ (degrees)

Intensity (arb. units)

v ZrO2

o

fluorite-type crystals *o Ni,Ti:ZnAl O

o

o 800 C/6h+ o 1200 C/6h o 800 C/6h+ o 1000 C/6h o 800 C/6h

2 4

o

v v o v v v o o

o ovv o

*

** * **

o 780 C/6h

~450

o

o

v

as-cast

2NiO

2.0%NiO

+ ZrTiO4

o

b

3.0%NiO

0.02 0.02 0.02 0.02 0.02

after heat-treatment at 950–1000 °C the gahnite lattice parameter firstly increases (a = 8.103 ± 0.002 Å) and then remains near constant (Fig. 6a). The gahnite mean size increases from about 8 nm to 20 nm as the heat-treatment temperature increases from 800 to 1100 °C. The size of ZrTiO4 crystal changes from 3 to 11 nm while ZrO2 crystals appeared at 1100 °C have a size of about 12 nm (Fig. 6b). The unknown crystalline phase quite different from those crystallized in glasses doped with 0–0.1 mol% NiO is found in glasses doped

0/0.1NiO

3.2.1. XRD data According to XRD analysis of glasses doped with 0 and 0.1 mol% NiO, crystals of ZrTiO4 and gahnite precipitate simultaneously after heat-treatments at above 750 °C for 6 h (Fig. 5a). Gahnite crystals exist within the whole temperature range under study (up to 1200 °C) while crystals of tetragonal ZrO2 appear instead of ZrTiO4 during heattreatment at 1100 °C. With an increase of heat-treatment temperature the integrated peak intensity of gahnite increases rapidly in the temperature range of about 800–950 °C and almost comes to saturation after heat treatments at higher temperatures. Gahnite crystal has a normal spinel structure, its lattice parameter a = 8.086 Å [35]. In the undoped glass-ceramics prepared by heattreatment at 800 °C the gahnite lattice parameter a = 8.085 ± 0.002 Å, it slightly increases with temperature and becomes equal to 8.102 ± 0.002 Å after heat-treatment at 1100 °C (Fig. 6a). In case of glass doped with 0.1 mol% NiO and heat-treated at 800 °C, gahnite lattice parameter is slightly larger than that for the undoped glass, a = 8.091 ± 0.002 Å,

± ± ± ± ±

Glasses NN 2–6 contain nucleating agents, TiO2 and ZrO2.

3.2. Glass-ceramics

Intensity (arb. units)

± ± ± ± ± ±

1.0%NiO

o

o

o o

vv o o

ovv o

o o

vv

* o* o* * * *

o

o o

as-cast

800

0.1%NiO 920 0NiO

200

400

600

800

Raman shift

1000

1200

1400

(cm-1)

Fig. 4. Raman spectra of parent glasses. The values indicated in the figure denote the NiO concentration (mol%) and frequencies corresponding to maximums of the Raman bands.

10

20

30

40

50

60

70

80

2θ (degrees) Fig. 5. X-ray diffraction patterns of parent and heat-treated glasses with (a) 0/0.1 and (b) 2 mol% NiO. The values indicated in the figure denote heat treatment schedules. The lower curve corresponds to the parent glass. The symbols “v”, “+”, “*” and “o” denote the diffraction lines attributed to ZrO2, ZrTiO4, xNiO⋅yTiO2⋅zZrO2 crystals with fluorite-type structure and gahnite ss (Ni,Zn:ZnAl2O4), respectively.

Please cite this article as: I.P. Alekseeva, et al., Influence of NiO on phase transformations and optical properties of ZnO–Al2O3–SiO2 glass-ceramics nucleated by TiO2 and..., J. Non-Cryst. Solids (2013), http://dx.doi.org/10.1016/j.jnoncrysol.2013.05.038

I.P. Alekseeva et al. / Journal of Non-Crystalline Solids xxx (2013) xxx–xxx

5

8,14

1,8

8,12

a (Ni,Ti):ZnAl2O4

8,08

0NiO 0.1NiO

1,4

solid solution 1,2

8,06

1,0 8,04

0,8 0,6

8,02

x= 950

1000

1050

1,6

Lattice constant a (Å)

1,6

XRD intensity (arb. units)

1,8

8,10

8,10

0,8 0,6

x= 900 950 1000 1050 1100 1150 1200 0,4

o o 800 C/6h+x C/6h

o 800 C/6h

500 0.1NiO 0NiO

Diameter (Å)

(Ni,Ti):ZnAl2O4 solid solution

100

Diameter (Å)

400

ZrO2

1,2

8,04

1100 0,4

150

solid solution

1,0

Heat-treatment mode

200

1,4

8,06

8,00

b

Ni,Ti:ZnAl2O4

8,02

8,00

o 800 C/6h

1NiO 2NiO 3NiO

8,08

XRD intensity (arb. units)

2,0

8,12

Lattice constant a (Å)

2,0

a'

o o 800 C/6h+x C/6h Heat-treatment mode

b' , , ,

1NiO 2NiO 3NiO

Ni:ZnAl2O4 300

solid solution

200

ZrO2 50

ZrTiO4 x= 950

1000

100 1050

x= 900 950 1000 1050 1100 1150 1200

1100

0

0

o 800 C/6h

o o 800 C/6h+x C/6h

Heat-treatment mode

o 800 C/6h

o o 800 C/6h+x C/6h

Heat-treatment mode

Fig. 6. Variation of lattice parameters and relative amount of gahnite solid solution (a, a′), diameter of crystals of gahnite ss, ZrTiO4 and ZrO2 (b, b′) with heat-treatment mode for glass-ceramics doped with 0 and 0.1 mol% NiO (a, b); 1–3 mol% NiO (a′, b′).

with 1–3 mol% NiO at low-temperature heat-treatments in the range of 730–800 °C (Fig. 5b). At elevated temperatures the character of crystallization of glasses with small and large content of NiO is very similar; the only exception is that in glasses with high content of NiO, tetragonal ZrO2 crystallizes instead of ZrTiO4 at above 800 °C. In glasses heat-treated from 800 °C to 1200 °C, gahnite crystals with sizes of 8–50 nm coexist with ZrO2 crystals with sizes of 7–40 nm (Figs. 5b, 6b′). The crystal sizes of gahnite and ZrO2 increase with the increase in NiO doping level (Fig. 6a). The gahnite lattice parameter a is almost the same for all Ni-containing glasses heat-treated at 800 °C for 6 h, it rapidly increases with heat-treatment temperature and then almost saturates (Fig. 6a′). At elevated temperatures, the higher the NiO content, the higher the lattice parameter a of gahnite (Fig. 6a′). With an increase of heat treatment temperature the integrated peak intensity of gahnite rapidly increases and then remains almost unchanged (Fig. 6a′), it increases with increasing the NiO content. 3.2.2. Absorption spectra The glasses doped with 0.1 mol% NiO and heat-treated at 730– 750 °C and the glasses doped with 1–3 mol% NiO and heat-treated at 730–780 °C exhibit a slight color change from deep brown-red to a lighter color (insets of Fig. 7a, b). In glass doped with 0.1 mol% NiO this heat-treatment results in a slight decrease of intensity of

the most strong absorption band located at 430 nm. Positions and intensities of the other bands remain practically unchanged probably due to a very small impact of new absorption centers on these bands (Fig. 7a, curve 2). It is difficult to assign this slight color change to certain color centers. Contrary to glass doped with 0.1 mol% NiO, glasses containing 1–3 mol% NiO after heat-treatments at 730–780 °C exhibit a distinct spectral change. The new spectrum appears (Fig. 7b, curve 2), which is characteristic of superposition of the Ni2+ absorption in the parent glass and a spectrum of Ni2+ ions in six-fold coordinated sites located in a stronger ligand field than in the parent glass [32] (this spectrum corresponds to precipitation of the unknown crystalline phase (Fig. 5b)). This spectrum is analyzed in detail in [32]. The color and, consequently, absorption spectra of glasses drastically change during heat-treatment at 800 °C, the temperature at that gahnite crystallizes (Fig. 7a, b, curves 3). Absorption spectra of glass-ceramics with a broad band in the near IR centered at about ~ 1050 nm and a wide asymmetric band in the visible region centered at about 660 nm are typical for Ni-doped spinels [20,26,36–38]. With increasing the heat-treatment temperature, absorption band in the visible spectral range acquires a complex structure while the position of the IR band slightly shifts to shorter wavelengths; there is no significant increase of peak intensities. Both bands are assigned to superposition of absorption of Ni2+ ions located in gahnite nanocrystals in sites with octahedral and tetrahedral symmetry, which is consistent

Please cite this article as: I.P. Alekseeva, et al., Influence of NiO on phase transformations and optical properties of ZnO–Al2O3–SiO2 glass-ceramics nucleated by TiO2 and..., J. Non-Cryst. Solids (2013), http://dx.doi.org/10.1016/j.jnoncrysol.2013.05.038

6

I.P. Alekseeva et al. / Journal of Non-Crystalline Solids xxx (2013) xxx–xxx

6

a

0.1NiO

1

4

parent glass

2

3.2.4. Raman spectroscopy data

Absorption coefficient (cm-1)

0 6

2

4

o

750 C/12h

2 0 1,2

3

0,8 o

800 C/6h

0,4 0,0

4

1,2 0,8

o

800 C/6h+ o 1100 C/6h

0,4 0,0

400

800

1200

1600

Wavelength (nm) 30

1

18 12

parent glass

6

Absorption coefficient (cm-1)

b

1NiO

24

0 20

2

15 10

o

780 C/6h

5 0 8

3

6 4

o

800 C/6h

2 0 8

4

6

o

4

3.2.4.1. Glass-ceramic samples. Raman spectra of parent and heattreated glasses are shown in Figs. 9 and 10. Fig. 9a demonstrates changes in Raman spectra of undoped glass with heat-treatment temperature (spectra of samples doped with 0.1 mol% NiO are similar to them). After heat-treatment of parent glass at 780 °C for 6 h, intensity of the ~ 920 cm−1 band in its Raman spectrum diminishes while intensity of the ~ 790 cm−1 band goes up; the spectral features of ZrTiO4 [40–42] and ZrO2 [43] crystals are clearly seen in the spectra (Fig. 9a) (the characteristic bands partly overlap and locate at ~ 148, 285, 334, 409 and 490 cm−1). Taking into account that Raman spectra are more sensitive to precipitation of ZrO2 and less sensitive to precipitation of gahnite than XRD patterns, these findings are in a good agreement with XRD data (Fig. 5a). The heat-treatment temperature increasing to 800 °C (Fig. 9) causes a further rise of the band at ~ 800 cm−1 and bands connected with continuous precipitation of ZrO2 and ZrTiO4. The bands typical for gahnite crystals appear at 417 and 657 cm−1 [44–46]. Intensity of gahnite bands rises with heattreatment temperature (Fig. 9). After a two-stage heat-treatment 800 °C/6 h + 1050 °C/6 h crystals of ZrTiO4 are not seen in the Raman spectrum any more while three new bands appear at ~ 720, 940 and 1100 cm− 1. For samples heat-treated in the temperature range of 1050–1200 °C (Fig. 8), intensity of all previously observed bands increases, bands connected with precipitation of ZrTiO4 crystals reappear in the spectrum. Raman spectra of glasses doped with 1–3 mol% NiO are similar to each other. Fig. 9b demonstrates Raman spectra of glass and glassceramics doped with 3 mol% NiO. The Raman band at 920 cm−1 weakens and the band at ~ 800 cm−1 is enhanced after heattreatment in the temperature range of 730–780 °C; no new bands appear in spectra. The increase of the heat-treatment temperature to 800 °C leads to a further enhancement of the band at 790 cm−1, appearance of bands at ~ 417 and ~ 659 cm−1 characteristic for gahnite crystals and broad bands of low intensity characteristic for beginning of precipitation of ZrO2. Intensities of bands connected with precipitation of gahnite and ZrO2 increase with increasing the heattreatment temperature (Fig. 9b) while the broad band at ~790 cm−1 becomes asymmetric because of the appearance of the new Raman

800 C/6h+ o 1100 C/6h

2 0

in the region of 1050–1600 nm. Its intensity increases with heattreatment temperature (Fig. 8). This luminescence is related with radiative transition for Ni2 + ions located in octahedral sites in gahnite crystals [32].

400

800

1200

1600

800/6 +1100/6

2000

Fig. 7. Absorption spectra of parent and heat-treated glasses doped with (a) 0.1 mol% NiO; (b) 1.0 mol% NiO. The values indicated in the figure denote the heat-treatment schedules. Insets represent images of polished samples. (For interpretation of the references to color in this figure, the reader is referred to the web version of this article.)

with a partly inverse structure of Ni-doped gahnite crystals [36 and references therein, 39]. The detailed assignment of absorption bands of Ni2+-ions in these spectra is made in [32]. 3.2.3. Luminescence spectra No near-IR luminescence was observed for all parent glasses and glass-ceramics heat-treated at 730–750 °C for 6–12 h (for samples doped with 0.1 mol% NiO) and at 730–780 °C for 6–72 h (for samples doped with 1–3 mol% NiO). However, heat-treatment of samples at higher temperatures (up to 1100 °C) results in intense luminescence

Intensity (arb. units)

Wavelength (nm)

800/6 +950/6

800/6 +900/6

800/6 1000

1100

1200

1300

1400

1500

1600

1700

Wavelength (nm) Fig. 8. Luminescence spectra of glasses with 1 mol% NiO in dependence on heat-treatment conditions. Excitation wavelength is 960 nm.

Please cite this article as: I.P. Alekseeva, et al., Influence of NiO on phase transformations and optical properties of ZnO–Al2O3–SiO2 glass-ceramics nucleated by TiO2 and..., J. Non-Cryst. Solids (2013), http://dx.doi.org/10.1016/j.jnoncrysol.2013.05.038

I.P. Alekseeva et al. / Journal of Non-Crystalline Solids xxx (2013) xxx–xxx

a

0/0.1NiO

Intensity (arb. units)

+

v

a

Ο

v - ZrO2

+

Ο

+

7

750 °C /24 h

+ - ZrTiO4

v

Ο -Ni,Ti:ZnAl2O4

~400

+ +

+ Ο

~640 ~538 ~589

v ~162

o o 800 C/6 h+1200 C/6 h

319

v

276

v ~720

~450

o o 800 C/6 h+1050 C/6 h

~603 417

v+

v

+

~940

+

v

~148 ~285 ~334

~1100

o o 800 C/6 h+900 C/6 h

~409

657

Intensity (a.u.)

v 330

v+

3.0NiO

2.0NiO

o 800 C/6 h

~490

o 780 C/6 h

1.0NiO

~435

~790

200

400

600

800

3NiO

1000

1200

1400

200

400

600

v

b

+ - ZrTiO4 Ο -Ni,Ti:ZnAl2O4

Ο

− ZrSiO4

~440

v 223

Ο

v v

563

v ~185

+v

o

955 978 1010

~709

~280

o

o

800 C/6 h+1050 C/6 h ~319 ~940

417 ~448

~1100 o

758

o

800 C/6 h+900 C/6 h

~485

1200

1400

v - ZrO2

Ο

+ - ZrTiO4

v

o

800 C/6 h+1200 C/6 h

Ο

1000

(cm-1)

800°C/6 h

v

663

358 408

+ v

Intensity (a.u.)

Intensity (arb. units)

+

0.0NiO

Ο

v - ZrO2

Ο

+v v

800

Raman shift

Ο Ο

920

parent glass

~920

Raman shift (cm-1)

b

0.1NiO

~790

~460

0

+

Ο662

Ni,Ti:ZnAl2O4

Ο

3.0NiO

417 ~602

2.0NiO

~330 ~484

~148 ~603

o

659

284

148

800 C/6 h

1.0NiO

o

750 C/24 h ~460

790

920

790

657

0.1NiO

parent glass

0

0.0NiO

200

400

600

800

1000

1200

1400

0

200

Raman shift (cm-1)

400

600

800

Raman shift Fig. 9. Raman spectra of parent and heat-treated glasses doped with (a) 0/0.1 mol% NiO; (b) 3 mol% NiO. The values indicated in the figure denote the heat-treatment schedules. The symbols “v”, “+”, “o” and “□” denote the bands attributed to ZrO2, ZrTiO4, gahnite solid solution (Ni,Ti:ZnAl2O4) and zircon (ZrSiO4), respectively.

1000

1200

1400

(cm-1)

Ο

c

Ο

800 oC/6 h+1050 oC/6 h v Ο

v

v - ZrO2 + - ZrTiO4

v

band at 758 cm−1. In the spectrum of the sample heat-treated at 800 °C/6 h + 1050 °C/6 the band at 758 cm−1 dominates. In addition to bands connected with gahnite and ZrO2 crystals the bands of ZrTiO4 and bands of very low intensity at 709, 940 and 1100 cm−1 become noticeable. After heat-treatment at 800 °C/6 h + 1200 °C/6 h the bands characteristic for zircon, ZrSiO4, appear in the spectrum at 223, 358, 440, 978 and 1010 cm−1 while the gahnite band at 659 cm−1 becomes broader and shifts to 663 cm−1. The influence of the addition of NiO on the phase transformations in zinc-aluminosilicate glasses is demonstrated in Fig. 10. In Raman spectra of glasses heat-treated at 750 °C for 24 h (Fig. 10a) redistribution of intensities of the bands located in the high-frequency region in favor of the band at 790 cm−1 is becoming more and more noticeable with the increase of NiO content. It allows to conclude that the addition of NiO accelerates the phase separation of parent glasses. According to Raman spectroscopy data, phase separation of glass is almost completed after heat-treatment at 800 °C for 6 h, as evidenced by the almost complete disappearance of the band at ~920 cm−1 and significant intensification of the band at 790 cm−1 (Fig. 10b). In spectra of all samples besides the bands of ZrO2 (148, 284, ~484 and ~ 602 cm−1) and ZrTiO4 (148, 284, 330 and 409 cm−1), there are gahnite bands at 417 and 657 cm−1 (Fig. 10b). With increasing the NiO content to 3 mol% intensity of all these bands decreases noticeably. The gahnite band located at 417 cm−1 becomes almost invisible, and the second band shifts from 657 to 663 cm−1.

Intensity (a.u.)

+v Ο +v

Ο

662

v

v

- Ni,Ti:ZnAl2O4

660

3.0NiO 758

~185 ~280

2.0NiO

~710 Ο

~448 417 ~484

319

148 ~603

657

~720

1.0NiO

780

0.1NiO 0.0NiO

200

400

600

800

1000

1200

1400

-1)

Raman shift (cm

Fig. 10. Raman spectra of glasses heat-treated at (a) 750 °C for 24 h; (b) 800 °C for 6 h, (c) 800 °C for 6 h and 1050 °C for 6 h. The values indicated in the figure denote the concentration of NiO. The symbols “v”, “+” and “o” denote the bands attributed to ZrO2, ZrTiO4 and Ni,Ti:ZnAl2O4, respectively.

Thus, based on Raman spectroscopy data, one may conclude that introduction of NiO accelerates the phase decomposition of glasses and slows down crystallization of zirconium dioxide, zirconium titanate and gahnite. After heat-treatment at 1050 °С, the broad high-frequency band previously located at ~ 790 cm−1 shifts to 780 cm−1 (Fig. 10c). An

Please cite this article as: I.P. Alekseeva, et al., Influence of NiO on phase transformations and optical properties of ZnO–Al2O3–SiO2 glass-ceramics nucleated by TiO2 and..., J. Non-Cryst. Solids (2013), http://dx.doi.org/10.1016/j.jnoncrysol.2013.05.038

8

I.P. Alekseeva et al. / Journal of Non-Crystalline Solids xxx (2013) xxx–xxx

increase of the NiO content results in a decrease of intensity in the maximum of the band at 417 cm−1 as compared with that of the band at 657 cm−1. The latter one shifts to 663 cm−1 while its FWHM and integrated intensity increase twice. The new Raman band appears at 758 cm−1, its intensity increases with increasing the NiO content. Additional peaks of low intensity are seen at 720 cm−1 (in spectra of glass-ceramics doped with 0–0.1 mol% NiO) or at 710 cm−1 (in spectra of glass-ceramics doped with 1–3 mol% NiO).

structure. Nickel is one of the components of this phase because the higher the NiO content, the lower the crystallization temperature (see Fig. 11a); the crystallinity fraction increases with NiO concentration (see Fig. 11b). In addition even more important is that there is a

o

a

730 C/48 h

*

* - fluorite-type structure

3NiO

2NiO

1NiO

0.1NiO 0NiO

10

20

30

40

50

60

70

80

2θ (degree) o

*

b

780 C/6 h

Intensity (arb. units)

*

*

*

* +o

* - fluorite-type structure o - ZnAl2O4 + - ZrTiO4

**

*

*

*

*

*

*

* * +

3NiO

2NiO 1NiO

o +

+

o ++

+ o

0NiO

0 10

20

30

40

50

60

70

80

2θ (degree)

c

o

*

3% NiO v

*

o

*

Intensity (arb.units)

All parent glasses were X-ray amorphous and inhomogeneous. They demonstrate the bimodal structure, i.e. the appearance of inhomogeneous regions with large and small sizes and different compositions. These regions develop in parent glasses upon cooling the melt and annealing of the glass. These data are in conformity with findings of C. Fernandez-Martin et al. [47] as they demonstrated a striking phase separation in the parent glass of magnesium-zinc aluminosilicate system nucleated by titania and zirconia. The addition of NiO promotes phase separation of parent glasses. Inhomogeneous regions containing NiO are uniformly distributed within the parent glass. An increase of the NiO content results in the growth of SAXS intensity by inhomogeneous regions. The average distance between the regions is independent of the NiO content. It means that NiO does not play a role of additional nucleating agent in these glasses containing large amounts of TiO2 and ZrO2, as it does not produce new scattering centers. The processes of phase transformations are different for glasses doped with 0–0.1 and 1–3 mol% NiO. In glasses containing 0–0.1 mol% NiO, ZrTiO4 and gahnite crystals precipitated simultaneously starting from heat-treatment at above 730–750 °C (depending on its duration). In glasses doped with 1–3 mol% NiO heat-treated in the temperature range of 730–780 °C crystals of ZrTiO4 and gahnite were not found while the unknown crystalline phase with fluorite-type structure appeared. It has sizes of 4–5 nm. Small lattice parameter of this fluorite-type phase (Table 2) as well as a pronounced increase of intensity of its XRD peaks with increasing the NiO content allows to suggest that this phase is based on ZrO2 stuffed with NiO and TiO2 (in the temperature range of its crystallization, there is no other phase containing ZrO2 and TiO2). For its identification we referred to investigation of G. Bayer [48] who demonstrated that MgO stabilizes ZrO2 in the fluorite-type structure. In MgO-stabilized ZrO2 up to 50 mol% ZrO2 could be replaced by TiO2. The amount of TiO2 which could be substituted for ZrO2 increased with increasing MgO concentration; the possibility for octahedral oxygen coordination increases in the same way. This substitution results in a large decrease in lattice constant of ZrO2, for instance, a = 4.905 Å for the composition MgO⋅ZrO2⋅TiO2 (mol%) and decreases with increasing MgO and TiO2 content in ZrO2 [48]. Ionic radius of Mg2+ in octahedral coordination is 0.72 Å, and that of Ni2+ is 0.69 Å. Thus possible substitution of Ni2+ for Mg2+ should result in a further decrease of the lattice parameter. We believe that the low-temperature metastable phase crystallized in glasses doped with 1–3 mol% NiO in the temperature range of 750–800 °C is nickel titanate-zirconate with fluorite-type

Intensity (arb. units)

4. Discussion

*

* - fluorite-type structure o - (Ni,Zn):ZnAl2O4 o v - ZrO2 *o *o * o o 800/6 v v

* **

*

**

*

*

*

780/6

*

750/24

*

**

750/12

*

*

730/48 Table 2 Lattice parameter a (Å) of the nickel titanate-zirconate with fluorite structure. Glass designation

Heat-treatment schedule °C/h 750/24

750/48

720/6 10

780/6

800/6

Glass doped with 4.879 ± 0.002 4.828 ± 0.002 4.792 ± 0.002 4.742 ± 0.002 1 mol% NiO Glass doped with 4.736 ± 0.002 4.734 ± 0.002 4.723 ± 0.002 4.715 ± 0.002 2 mol% NiO Glass doped with 4.714 ± 0.002 4.705 ± 0.002 4.695 ± 0.002 4.687 ± 0.002 3 mol% NiO

20

30

40

50

60

70

80

2θ (degree) Fig. 11. X-ray diffraction patterns of glasses heat-treated (a) at 730 °C for 48 h and (b) at 780 °C for 6 h. The values indicated in the figure denote the NiO content. (c) X-ray diffraction patterns of heat-treated glass doped with 3 mol% NiO. The values indicated in the figure denote heat treatment schedules. The symbols “*”,“o”, “+”, and “v” denote the diffraction lines attributed to nickel titanate-zirconate with fluorite-type structure, ZnAl2O4, ZrTiO4 and ZrO2, respectively.

Please cite this article as: I.P. Alekseeva, et al., Influence of NiO on phase transformations and optical properties of ZnO–Al2O3–SiO2 glass-ceramics nucleated by TiO2 and..., J. Non-Cryst. Solids (2013), http://dx.doi.org/10.1016/j.jnoncrysol.2013.05.038

I.P. Alekseeva et al. / Journal of Non-Crystalline Solids xxx (2013) xxx–xxx

substantial change in absorption spectra of glasses after crystallization of this phase (Fig. 7b, curve 2) because of the formation of octahedrally coordinated Ni2+ ions located in a stronger ligand field than in parent glasses [32]. Raman spectra of these glass-ceramics do not contradict to the assumption of precipitation of crystals with fluorite-type structure. Fig. 9a shows that a weak broad band located in the range of 200–350 cm−1 is superimposed on the low-frequency slope of the broad band of zinc-aluminosilicate glass ~ 435 cm−1. Similar broad band was observed in Raman spectra of compounds with fluorite structure [49]. Thus the experimental observation based on Raman spectroscopy data that introduction of NiO accelerates the phase decomposition of glasses and slows down crystallization of zirconium dioxide, zirconium titanate and gahnite is connected with precipitation of fluorite-type crystals instead of zirconium titanate and gahnite. Upon heat-treatments at above 800 °С this broad band disappears. The bands characteristic of gahnite and tetragonal ZrO2 crystals appear in the Raman spectrum (Fig. 9b). The evolution of this crystalline phase is shown in Fig. 11c by means of XRD data. The lattice parameter of gahnite crystals precipitated in samples of all compositions under study is much larger than in gahnite single crystals; and it increases with increasing the content of NiO. Judging from the absorption spectra of gahnite-based glass-ceramics (Fig. 7, curves 3, 4), Ni-ions enter the gahnite structure; the intense near IR luminescence of such samples speaks about Ni2+ doping of gahnite with the substitution for Al3 + in octahedral sites [32]. However the lattice parameter of NiAl2O4 (a = 8.0478 Å [26]) is less than that of gahnite and the addition of Ni2+ should result in a decrease of the gahnite lattice parameter. We explain this behavior of the unit cell parameter by Ti4+doping of gahnite with the substitution for Al3+ in octahedral sites, which caused an increase of the unit cell parameter [50]. We suggest that Ni2+ ions enter the gahnite crystals together with Ti4+ substituting for Al3+ in octahedral sites. Raman spectra of glass-ceramics confirm this assumption. According to group theory, cubic spinels (Fd3m) have five Raman-active phonon modes [44]. As a rule, they give three most strong Raman bands at ~400, ~670 and ~770 cm−1. In the gahnite spectrum the highfrequency band is much weaker than the others. There is only one experimental Raman spectrum of gahnite that demonstrates this band located at 758 cm−1 [44]; the gahnite mineral with composition (Zn0.83Fe0.11 Mg0.06)Σ = 1(Al0.96Fe0.04)Σ = 2O4 also has a similar band [51]. These gahnite spectra also contain a very weak band at 708 cm−1 [44,51]. Together with other gahnite intense bands, these two bands are observed in the Raman spectra of glass-ceramics doped with 1–3 mol% NiO. The higher the NiO content in glass-ceramics, the lower the heat-treatment temperature that results in the Raman band at 758 cm−1. For glass-ceramics doped with 1, 2 and 3 mol% NiO this temperature is 1050, 900 and 850 °С, respectively. Enhancement of the Raman band at 758 cm− 1 in spectra of glass-ceramics is attributed to entering the titanium ions into gahnite crystals, the number of embedded titanium ions increases with the increase of the NiO content. To support this assumption, we prepared various model compounds with spinel structure. The Raman spectrum of the model compound with the composition 2ZnAl2O4 + NiZnTiO4 sintered at 1250 °С for 24 h has not only the gahnite bands at 417 and 663 cm−1 but also a strong band at 758 cm−1 and a weak band at 708 cm−1. It is worth mentioning that entering the titanium ions into gahnite crystals in glass-ceramics with high content of NiO results in the precipitation of ZrO2 instead of ZrTiO4. Appearance of weak high-frequency bands at 940 and 1100 cm−1 in spectra of all glass-ceramics prepared by high-temperature heat-treatments is connected with vibrations of [TiO4] groupings in the residual highly siliceous glass [30]. Crystallization of Ni-doped gahnite results in intense luminescence in the region of 1050–1600 nm (Fig. 8). This luminescence is related with radiative transition for Ni2+ ions located in octahedral sites in gahnite crystals [32]. The above mentioned findings will help

9

us to analyze physical mechanisms that govern the luminescence properties of nickel-doped nanophase glass-ceramics of zinc-aluminosilicate system, which is the subject of the second part of this paper. 5. Conclusions Parent glasses are inhomogeneous and X-ray amorphous. They possess the bimodal structure; the distance between the inhomogeneous regions is independent of the NiO content implying that NiO does not play a role of additional nucleating agent in glass with large contents of TiO2 and ZrO2. The addition of NiO facilitates phase separation of the parent glasses. Increased NiO content promotes not only liquid phase-separation of parent glasses but also crystallization of a new crystalline phase of nickel titanate-zirconate with fluorite-type structure. There is a difference in behavior of glasses doped with 0–0.1 mol% NiO and 1–3 mol% NiO. In glasses doped with 0–0.1 mol% NiO, ZrTiO4 and Ni,Ti-doped gahnite crystals precipitated simultaneously starting from heat-treatment at above 730 °C; traces of ZrO2 tetragonal crystals were found in glass-ceramics prepared at 1000–1200 °C. In glasses doped with 1–3 mol% NiO crystals of nickel titanatezirconate with fluorite-type structure are formed as a primary phase at 730–780 °C. They decompose at elevated temperatures above 800 °C with the formation of Ni,Ti-doped gahnite and ZrO2 nanosized crystals. Acknowledgments This work was partly supported by the RFBR (Grants 12-02-01263, 12-02-00938 and 13-03-01289) and the Ministry of Education and Science of the Russian Federation (Projects 11.519.11.3020, 11.519.11.3026, 14.B37.21.0741 and 14.В37.21.1954). The authors wish to express their deep gratitude to Mr. Bogdanov for recording the Raman spectra. References [1] O.S. Dymshits, A.A. Zhilin, M.Ya. Tsenter, T.I. Chuvaeva, Glass Phys. Chem. 17 (1) (1991) 87, (in Russian). [2] O.S. Dymshits, A.A. Zhilin, V.I. Petrov, M.Ya. Tsenter, T.I. Chuvaeva, V.V. Golubkov, Glass Phys. Chem. 24 (1998) 79. [3] S.J. Bae, U. Kang, O. Dymshits, A. Shashkin, M. Tsenter, A. Zhilin, J. Non-Cryst. Solids 351 (37–39) (2005) 2969. [4] I. Alekseeva, O. Dymshits, M. Tsenter, A. Zhilin, J. Non-Cryst. Solids 357 (11–13) (2011) 2209. [5] V.V. Golubkov, T.I. Chuvaeva, O.S. Dymshits, A.A. Shashkin, A.A. Zhilin, W.-B. Byun, K.-H. Lee, J. Non-Cryst. Solids 345–346 (2004) 187. [6] V.V. Golubkov, O.S. Dymshits, A.A. Zhilin, T.I. Chuvaeva, A.V. Shashkin, Glas. Phys. Chem. 30 (4) (2004) 300. [7] V.V. Golubkov, O.S. Dymshits, A.V. Shashkin, A.A. Zhilin, Phys. Chem. Glasses Eur. J. Glass Sci. Technol. B 48 (4) (2007) 276. [8] I. Alekseeva, A. Baranov, O. Dymshits, V. Ermakov, V. Golubkov, M. Tsenter, A. Zhilin, J. Non-Cryst. Solids 357 (2011) 3928. [9] L.F. Johnson, H.J. Guggenheim, D. Bahnck, A.M. Johnson, Opt. Lett. 8 (1983) 371. [10] W.E. Vehse, K.H. Lee, S.I. Yun, W.A. Sibley, J. Lumin. 10 (1975) 149. [11] J.F. Donegan, G.P. Morgan, T.J. Glinn, G. Walker, J. Mod. Opt. 4 (37) (1990) 769. [12] J.F. Donean, F.J. Bergin, T.J. Glynn, G.F. Imbusch, J. Lumin. 1 (35) (1986) 57. [13] N.V. Kuleshov, V.G. Shcherbitsky, V.P. Mikhailov, S. Kuck, J. Koetke, K. Petermann, G. Huber, J. Lumin. 71 (1997) 265. [14] S. Kück, Laser-related spectroscopy of ion-doped crystals for tunable solid state-lasers, Appl. Phys. B 72 (2001) 515, (and references therein). [15] B.N. Samson, L.R. Pinckney, J. Wang, G.H. Beall, N.F. Borrelli, Opt. Lett. 15 (27) (2002) 1309. [16] L. Pinckney, G. Beall, Proc. SPIE 93 (2001), http://dx.doi.org/10.1117/12.446883. [17] T. Suzuki, Y. Ohishi, Appl. Phys. Lett. 84 (2004) 3804. [18] T. Suzuki, K. Horibuchi, Y. Ohishi, J. Non-Cryst. Solids 351 (2005) 2304. [19] B. Wu, J. Qiu, M. Peng, J. Ren, X. Jiang, C. Zhu, Mater. Res. Bull. 42 (2007) 762. [20] S. Zhou, J. Hao, J. Qiu, J. Am. Ceram. Soc. 9 (94) (2011) 2902. [21] S. Zhou, H. Dong, H. Zeng, B. Wu, B. Zhu, H. Yang, S. Xu, Z. Wang, J. Qiu, J. Appl. Phys. 102 (2007) 063106, (4 pp.). [22] V.N. Sigaev, N.V. Golubev, E.S. Ignat’eva, V.I. Savinkov, M. Campione, R. Lorenzi, F. Meinardi, A. Paleari, Nanotechnology 23 (2012) 015708, ((7 pp.) and references therein). [23] S.F. Zhou, H.F. Dong, G.F. Feng, B.T. Wu, H.P. Zeng, J.R. Qiu, Opt. Express 15 (2007) 5477.

Please cite this article as: I.P. Alekseeva, et al., Influence of NiO on phase transformations and optical properties of ZnO–Al2O3–SiO2 glass-ceramics nucleated by TiO2 and..., J. Non-Cryst. Solids (2013), http://dx.doi.org/10.1016/j.jnoncrysol.2013.05.038

10

I.P. Alekseeva et al. / Journal of Non-Crystalline Solids xxx (2013) xxx–xxx

[24] S.F. Zhou, N. Jiang, K. Miura, S. Tanabe, M. Shimizu, M. Sakakura, Y. Shimotsuma, M. Nishi, J. Qiu, K. Hirao, J. Am. Chem. Soc. 132 (50) (2010) 17945. [25] S.F. Zhou, N. Jiang, B. Wu, J. Hao, J. Qiu, Adv. Funct. Mater. 19 (2009) 2081. [26] P. Porta, F.S. Stone, R.G. Turner, J. Solid State Chem. 11 (1974) 135. [27] V.V. Golubkov, O.S. Dymshits, V.I. Petrov, A.V. Shashkin, M.Ya. Tsenter, A.A. Zhilin, U. Kang, J. Non-Cryst. Solids 351 (2005) 711. [28] V.N. Filippovich, J. Technic. Phys. 26 (2) (1956) 398, (in Russian). [29] H. Lipson, H. Steeple, in: McMillan (Ed.), Interpretation of X-ray Powder Patterns, Martins Press, London, N.Y., 1970. [30] I. Alekseeva, O. Dymshits, V. Ermakov, V. Golubkov, A. Malyarevich, M. Tsenter, A. Zhilin, K. Yumashev, Phys. Chem. Glasses Eur. J. Glass Sci. Technol. B 53 (4) (2012) 167–180. [31] L. Galoisy, G. Calas, Geochim. Cosmochim. Acta 57 (1993) 3613. [32] P.A. Loiko, O.S. Dymshits, A.A. Zhilin, I.P. Alekseeva, K.V. Yumashev, J. Non-Cryst. Solids 376 (2013) 99. [33] Ya.S. Bobovich, Opt. Spektrosk. 14 (5) (1963) 647–654, ([Opt. Spectrosc. (Engl. Transl.)]). [34] F.L. Galeener, A.J. Leadbetter, M.W. Stringfellow, Phys. Rev. B 27 (1983) 1052. [35] H.St.C. O'Neill, W.A. Dollase, Phys. Chem. Mineral. 20 (1994) 541. [36] D. Visinescu, F. Papa, A.C. Ianculescu, I. Balint, O. Carp, J. Nanopart. Res. 15 (2013) 1456, http://dx.doi.org/10.1007/s11051-013-1456-1.

[37] O.S. Dymshits, A.A. Zhilin, T.I. Chuvaeva, M.P. Shepilov, J. Non-Cryst. Solids 127 (1991) 44. [38] A. Dugué, L. Cormier, O. Dargaud, L. Galoisy, G. Calas, J. Am. Ceram. Soc. 95 (2012) 3483. [39] A. Navrotsky, Am. Mineral. 71 (1986) 1160. [40] M.A. Krebs, R.A. Condrate, J. Mater. Sci. Lett. 7 (1988) 1327. [41] F. Azough, R. Freer, J. Mater. Sci. 28 (1993) 2273. [42] A.A. Zhilin, V.I. Petrov, M.Ya. Tsenter, T.I. Chuvaeva, Opt. Spectrosc. 73 (6) (1992) 1151, (in Russian). [43] D.P.C. Thackeray, Spectrochim. Acta 30A (1974) 549. [44] A. Chopelas, A. Hofmeister, Phys. Chem. Miner. 18 (1991) 279. [45] C.M. Fang, C.K. Loong, G.A. de Wijs, G. de With, Phys. Rev. B 66 (14) (2002) 144301. [46] S. Lopez-Moreno, P. Rodrıguez-Hernandez, A. Munoz, A.H. Romero, F.J. Manjon, D. Errandonea, E. Rusu, V.V. Ursaki, Ann. Phys. (Berlin) 523 (1–2) (2011) 157. [47] C. Fernandez-Martin, G. Bruno, A. Crochet, D. Ovono Ovono, M. Comte, L. Hennet, J. Am. Ceram. Soc. 95 (2012) 1304. [48] G. Bayer, J. Amer. Ceram. Soc. 53 (1970) 294. [49] M. Glerup, O.F. Nielsen, F.W. Poulsen, J. Solid State Chem. 160 (2001) 25. [50] M. Vrankić, B. Gržeta, V. Mandić, E. Tkalčec, S. Milošević, M. Čeh, B. Rakvin, J. Alloys Compd. 543 (2012) 213–220. [51] http://rruff.info/gahnite/display=default/R040027.

Please cite this article as: I.P. Alekseeva, et al., Influence of NiO on phase transformations and optical properties of ZnO–Al2O3–SiO2 glass-ceramics nucleated by TiO2 and..., J. Non-Cryst. Solids (2013), http://dx.doi.org/10.1016/j.jnoncrysol.2013.05.038