Effect of replacement of B2O3 by ZnO on preparation and properties of transparent cordieri

Journal of Non-Crystalline Solids 432 (2016) 265–270

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Effect of replacement of B2O3 by ZnO on preparation and properties of transparent cordierite-based glass-ceramics Xiaojun Hao, Zhiwei Luo, Xiaolin Hu, Jun Song, Yu Tang, Anxian Lu ⁎ School of Materials Science and Engineering, Central South University, Changsha 410083, China

a r t i c l e

i n f o

Article history: Received 18 June 2015 Received in revised form 5 October 2015 Accepted 7 October 2015 Available online 22 October 2015 Keywords: Cordierite; Glass-ceramics; High crystallinity; Optical property

a b s t r a c t The effect of B2O3 replacement by different contents of ZnO on the preparation and various properties of transparent cordierite-based glass-ceramics was deeply investigated. With ZnO addition, the glass transition temperature (Tg) changed slightly, while the crystallization temperature (Tc) decreased greatly, which was confirmed by the DSC results. According to the X-ray diffraction and TEM analysis, ZnO affected the type of the crystal phases, as well as increased the crystallinity and changed the grain size. In addition, the transmittance, thermal expansion coefficient, Vickers hardness and bending strength of glass-ceramics were greatly influenced by the content of ZnO. Transparent glass-ceramics with excellent optical, thermal and physical properties were prepared by nucleating the sample with 2 mol% ZnO content at 820 °C for 6 h and then crystallizing it at 1000 °C for 6 h. © 2015 Elsevier B.V. All rights reserved.

1. Introduction Transparent glass-ceramics are still being widely used in the area of lasers and optical amplifiers until now due to their excellent optical properties, great thermal stability and high mechanical strength [1–3]. A large amount of investigations on transparent glass-ceramics have been published and these transparent crystalline materials have been applied widely in the last thirty years. However, the majority of traditional transparent glass-ceramics have nano-sized crystals and small to moderate crystallized volume fraction, which influenced their mechanical or thermal properties [4,5]. As opposed to the traditional transparent glass-ceramics, E.D. Zanotto et al. [5] developed a new type transparent glass-ceramics having large (micrometric) grain size and high crystallinity (97%) from Na2O–CaO–SiO2 system, and presented a novel method of fabricating transparent glass-ceramics with high crystallinity. Applications in multilayer ceramic packaging and ceramic–matrix composites [6,7], cordierite (Mg2Al4Si5O18) and cordierite-based glassceramics have been widely studied for their low thermal expansion coefficient, high thermal and chemical stability, as well as high mechanical strength [8,9], and many investigations on this system have been reported. Investigation concerned with the nucleation sites and kinetics of cordierite-type glass was reported by E.D. Zanotto et al. [10], and they pointed out that devitrification started from glass surface without ⁎ Corresponding author. E-mail addresses: [email protected], [email protected] (A. Lu).

http://dx.doi.org/10.1016/j.jnoncrysol.2015.10.017 0022-3093/© 2015 Elsevier B.V. All rights reserved.

nucleating agents as they were regions of higher energy due to tips, cracks, scratches and impurities. Hwang and Wu [11] studied the effect of composition on microstructural development in this system, and they concluded that compositions richer in SiO2 than the stoichiometric composition of cordierite enhanced the crystallization of α-cordierite, resulting in a higher content of α-cordierite. The addition of B2O3 to cordierite glass was extensively studied by several authors [12–15], they found that this additive played an important role in governing the crystallization behavior. Acting as a network modifier, ZnO can affect the crystallization and properties of many glass-ceramic systems greatly. The effect of ZnO on the properties of cordierite-based glass-ceramics was studied by Chen [16], he believed that addition of some amounts of ZnO impeded the formation of α-cordierite and accelerated the formation of gahnite, as well as increased the thermal expansion coefficient of glass-ceramics. Mirhadi et al. [17] investigated the effect of zinc oxide on microhardness and sintering behavior of MgO–Al2O3–SiO2 glass-ceramic system, they suggested that the replacement of MgO by ZnO promoted the precipitation of gahnite, as well as increased the density, sinterability and hardness. With more ZnO addition, the melting temperature and crystallization temperature of MgO–Al2O3–SiO2 system glass-ceramics decreased, and the predominant crystalline phase changed from α-cordierite to gahnite and quartz [18]. In this paper, the effect of replacement of B2O3 by ZnO on the preparation and various properties of transparent cordierite-based glassceramics was investigated, with the aim to improve its optical, thermal and mechanical properties.

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2. Experimental procedure 2.1. Preparation of materials Four different kinds of glass were prepared from high purity MgO, Al2O3, SiO2, H3BO3 and ZnO (≥99.99%) by melt quenching method. The compositions of these parent glass were close to the stoichiometric composition of cordierite (2MgO·2Al2O3·5SiO2), which are shown in Table 1. Proper batches of each powder were thoroughly mixed and then melted at 1560–1580 °C for 2 h in a platinum crucible in an electric furnace. The homogenous melts were poured onto a preheated stainless steel mold, and subsequently transferred into a muffle furnace and annealed at 680 °C for 2 h to remove the internal stress. The obtained clear and transparent glass were cut into the desired dimension, and then optically polished in order to perform different measurements.

temperature range of 20–600 °C at a heating rate of 5 °C/min. The final values were obtained by averaging the values among the temperature range of 20–600 °C. The hardness of glass-ceramics was carried out using a microhardness tester (DHV-1000-CCD, Beijing) with a pyramid shaped diamond indenter with loads of 4.9 N for 10 s. Five measurements were made on each glass-ceramics and were averaged. Bending strength of the glass-ceramics with dimensions of 5 mm × 5 mm × 25 mm was achieved by applying three point bending method through the DD-1100 machine at a cross-head speed of 5 mm/min. Final results were obtained by averaging five measurements of each of the samples. 3. Results and discussion 3.1. DSC analysis

2.2. Analytical methods DSC measurements were carried out on a differential scanning calorimetry (Netzsch 404PC, Germany) to determine the glass transition (Tg) and crystallized peak (Tc) temperatures of these parent glass under air atmosphere at a heating rate of 10 °C/min. Powdered samples weighing 10–15 mg were placed in an alumina crucible to conduct the DSC measurement during the temperature range of 30–1100 °C. The measurement error is ±2 °C. Mixed with KBr power, the infrared samples were prepared as homogeneous disks and then the FTIR measurements (Fourier transform infrared absorption spectra) of these samples were carried out in the range of 400–4000 cm−1 using a Thermo Scientific Nicolet 6700 FT-IR spectrophotometer. The crystalline phase precipitated in the glass-ceramics was identified by an X-ray diffractometer (XRD, D/max 2500 model, Rigaku, Japan) with Cu–Kα radiation (λ = 0.154 nm). The diffractometer scanned the powder at a rate of 8° min−1 within Bragg angle (2θ) from 5° to 80°. The crystalline phase was identified through matching the peak positions of the intense peaks with PDF standard cards. Besides, the crystallized volume fraction of glass-ceramics was calculated by Jade 6.0, within the error range of about ±5%. The transmission electron microscope (JEOL JEM 2100F) was used to characterize crystalline microstructure of glass-ceramics. Prior to TEM, the glass-ceramic samples were ground (less than 100 nm) and then dissolved into the alcohol solution homogeneously. Appropriate amount of solution was dropped on the copper film and then dried under an infrared lamp. The transmittance of the glass-ceramics was measured with a HITACHI U-3310 UV spectrophotometer (Hitachi Ltd., Japan) during the wavelength range of 200–780 nm. The surface of glass-ceramic sample was polished (2000 mesh) and cleaned by Ultrasonic Bath with alcohol as the clearing agent. The refractive index of parent glass was studied by an Abbe refractometer (2 W) with accuracy of nD ± 0.002. Density was determined by the Archimedes method with distilled water as the immersion medium at room temperature, ρ = m1ρ0/ (m1 − m2), where, m1 was the weight of the sample in the air, m2 was the weight of the sample in the distilled water, and the ρ0 was the density of the distilled water. The thermal expansion coefficient was obtained by a thermomechanical analyzer (Netzsch DIL 402EP, Germany) within the

The DSC curves of the parent glass samples containing various amount of ZnO are shown in Fig. 1. All glass powders initially exhibit a transition of glass at around 785 °C, and followed by the exothermic peaks which correspond to the crystallization from the parent glass. Close observation of the figure demonstrates that the glass transition temperature (Tg) increases with the increase of ZnO addition, though these changes are slight. However, the onset crystallization temperature (Tonset) and the exothermic peak temperature (Tp) have higher sensitivity to the content of ZnO, which decrease greatly with ZnO addition. Besides, only one exothermic peak occurs for the glass samples Z0–Z4, but two exothermic peaks appear when B2O3 is replaced by ZnO completely, implying that the doping of 5 mol% ZnO may cause the formation of two crystalline phases during heat treatment. The Tg, Tonset and Tp are listed in Table 2. The stability of glass against crystallization during crystallization can be evaluated by the Hrüby factor (KH) [19], KH ¼

T onset −T g T m −T onset

ð1Þ

here, Tm is the melting point of cordierite (1467 °C) [10]; Tonset and Tg can be determined from the DSC curve; The range of typical KH values is between 0.1 and 2, and the lower the value of KH, the more unstable the parent glass. Through calculation from Eq. (1), it is obvious that the KH decreases with ZnO addition, which suggests the ZnO breaks down the glass network and decreases the glass stability. In addition, the decrease of B2O3 content can enhance the crystallization tendency

Table 1 Chemical composition of parent glass (mol%). No.

MgO

Al2O3

SiO2

B2O3

ZnO

Z0 Z2 Z4 Z5

20 20 20 20

20 20 20 20

55 55 55 55

5 3 1 0

0 2 4 5

Fig. 1. DSC curves for glass samples treated at 10 k/min: (a) Z0; (b) Z2; (c) Z4; and (d) Z5.

X. Hao et al. / Journal of Non-Crystalline Solids 432 (2016) 265–270 Table 2 The thermal data of Z0, Z2, Z4 and Z5 glass samples. Glass code Tg (°C) Tonset (°C) Tp1 (°C) Tp2 (°C) △T = Tonset − Tg (°C) KH Z0 Z2 Z4 Z5

784 785 787 788

972 965 945 892

1008 994 978 913

– – – 969

188 180 158 104

0.380 0.359 0.303 0.180

of glass [14]. All of these factors can improve the diffusion of ions and may promote the precipitation of phases from the parent glass. In order to obtain the transparent glass-ceramics, the nucleation temperature of the sample was set at 820 °C for 6 h, and the crystallization temperature was chosen at 1000 °C for 3 h, 6 h and 9 h, respectively, according to the DSC results. 3.2. Effect of Zn2+ ion on the glass structure Fig. 2 displays the IR spectra of the four glass samples, and the characteristic peaks of different functional groups are marked in the figure. The bands near 450 cm−1 may be due to the bending vibration of Si–O–Si in [SiO4]-tetrahedron [20]. The appearance of the absorption at 700 cm−1 could be attributed to the symmetric stretching vibration of Al–O–Al bond in [AlO4]-tetrahedron [21]. The 800 cm−1 absorption peaks may be ascribed to Si–O–Si inter-tetrahedral bridging bonds in SiO2 [22]. In addition, the peaks near 940 cm−1 may be related with the vibration of Si–O− and the symmetric stretching vibration Si–O–Si bond, the absorption bonds observed at 1090 cm−1 corresponded to asymmetric stretching vibration of Si–O–Si bond in [SiO4]-tetrahedron [23]. What's more, peaks at 1430 cm− 1 was the vibration of B–O in [BO3]-triangle [24]. It is clear that the position and intensity of peaks change slightly with the increase of ZnO. The addition of ZnO leads to the depolymerization of glass framework, resulting in a large amount of nonsaturable Si–O−, so it is reasonable that the vibration of Si–O− and the Si–O–Si symmetric stretching band shift towards to the smaller wavenumber. Meanwhile, the “isolated” [AlO4]-tetrahedron increases due to the breakdown of glass network, which changes the connection among [AlO4] units, so the symmetric stretching vibration of Al–O–Al bond moves to lower wavenumber. As the B2O3 is replaced by ZnO gradually, the characteristics of vibration absorption peaks of [BO3]-triangle decrease until it vanish. All these changes above may identify the variations of Tg and Tp on the DSC curves.

Fig. 2. Fourier-transformed infrared spectra of glass batches: (a) Z0; (b) Z2; (c) Z4; and (d) Z5.

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According to DSC and IR spectra analyses, the introduction of ZnO did have an effect on the glass network, and it is reasonable to predict that ZnO can affect the crystallization behavior and the related properties of glass-ceramics. 3.3. Crystallization behavior of the glass-ceramics 3.3.1. Effect of heat-treatment on crystallization and phase formation Fig. 3 illustrates the X-ray patterns of 2 mol% ZnO sample crystallized at 1000°C for 3 h, 6 h and 9 h. Two crystal phases, μ-cordierite (Mg 2 (Al 4 Si 5 O 18 ), PDF No. 82-1541) and α-cordierite (Mg2(Al4Si5O18), indialite, PDF No. 82-1540), precipitate in parent glass after being crystallized at 1000 °C for 3 h. As the crystallization time is prolonged, it can be obviously seen that the position of the strongest peak changes from 29.46° to 10.40°, indicating that the μ-cordierite transforms into α-cordierite continuously until it vanishes. Compared with the α-cordierite, the μ-cordierite is a metastable phase, it is reasonable for it to be transformed into α-cordierite as the crystallization time is prolonged. In addition, the crystallized volume fraction of glass-ceramics was calculated by Jade 6.0, within the error range of about ± 5%. They are 80%, 92%, and 99%, respectively, which increase gradually following the increase of the crystallization time. The crystallization mechanism of parent glass has been discussed in our previous study [9], which was one-dimensional interfacial growth followed with surface nucleation. As the crystallization time is prolonged, the crystals devitrified on the sample surface initially and then grew towards the sample interior gradually until they meet the other growing plane (nucleated on the opposing surface). Thus, the sample crystallized for 3 h contains a large amount of residual glass in the interior of glass-ceramics, which can influence its mechanical or thermal properties. On the other hand, the grain size increases gradually as the crystallization time is prolonged and will have a great effect on the optical property of glass-ceramics. To sum up the analysis above, we may consider the process of heating at 1000 °C for 6 h as the ideal choice. 3.3.2. Effect of ZnO content on crystallization and phase formation According to the XRD analysis mentioned above, the four different glass samples were crystallized at 1000 °C for 6 h, and their powder XRD patterns are shown in Fig. 4. Casting a glance at the figure, the primary phase transforms from μ-cordierite into α-cordierite completely with the increase of ZnO content. Apart from α-cordierite, however,

Fig. 3. XRD patterns of glass sample with 2 mol% ZnO content crystallized at 1000 °C for different times: (a) 3 h; (b) 6 h; and (c) 9 h.

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Based on the DSC and IR analyses, the introduction of Zn2+ ions promote the transformation from μ-cordierite into α-cordierite, which has been identified in Fig. 4. Furthermore, as the addition of ZnO weakens the glass network and accelerates the diffusion of Mg2+ ions, it is reasonable to see the appearance of pyrope phase in Fig. 4 (c) and (d). The secondary phase not only impedes the formation of α-cordierite but also decreases the transparency of glass-ceramics greatly, so we should control the type and content of crystals that will precipitate in the glass-ceramics. Having compared the diffraction patterns of four different glass-ceramics, we consider the Z2 as the ideal sample under this heat-treatment condition. 3.4. Microstructure of the glass-ceramics

Fig. 4. XRD patterns of four samples containing different ZnO contents crystallized at 1000 °C for 6 h: (a) Z0; (b) Z2; (c) Z4; and (d) Z5.

another phase (Pyrope, Mg3Al2[SiO4]3, PDF No. 88-2202) appears and increases at higher ZnO content (4 and 5 mol%), which may result in the decrease of main phase as the preferential growth of crystal grains hinder the mobility of other ions. In addition to the type of crystal phases, the crystallinity of these four samples are greatly influenced by the ZnO content and they are 56%, 92%, 85%, and 87%, respectively. Moreover, the diffraction peaks of glass-ceramics vary, demonstrating that ZnO also have an effect on the grain size.

Glass-ceramics have a dense microcrystalline structure similar to that of ceramic materials based on pure oxides, and characterized by the randomly oriented crystals of a very small size, by the absence of porosity and by the linkage effect of glassy phase among crystals [25]. Fig. 5 shows the microstructure of the sample containing 2 mol% ZnO crystallized at 1000 °C for 6 h. It is well known to us that the grain can be observed clearly under the electron microscope when they have different contrast with the surrounding medium due to the different chemical compositions of both. However, as the crystal phases and residual glass phase have very similar chemical composition in our glass-ceramics, it is different when observing the grain clearly under the plane-view TEM. Close observation of the Fig. 5 (a) demonstrates that a large amount of lattice fringes occur in the red circle area. According to the plane-view TEM and the Fourier transform in Fig. 5 (b) of this area, we consider that a large amount of α-cordierite are well-dispersed in the glass matrix. Fig. 5 (c) is the HR-TEM micrographs for the side of the red circle area, showing a clear line between residual glass and the α-cordierite

Fig. 5. (a) is the plane-view TEM image for the sample containing 2 mol% ZnO crystallized at 1000 °C for 6 h, (b)–(d) are the Fourier transform, HR-TEM and EDS of the red circle area in the plane-view, respectively.

X. Hao et al. / Journal of Non-Crystalline Solids 432 (2016) 265–270

phases. Based on the analysis in our previous study [9] and the TEM results, the crystals may exhibit unidimensional morphology with size of about 30–40 nm. Combined with the XRD and TEM results, the sample with 2 mol% ZnO has high crystallinity, small grain and fine microstructure after being crystallized at 1000 °C for 6 h, which can endow the glassceramics with better related properties. 3.5. Optical property of the transparent glass-ceramics Fig. 6 displays the visible transmittance spectra and photographs of the samples containing different ZnO contents crystallized at 1000 °C for 6 h: (a) Z0; (b) Z2; and (c) Z4. It is evident from the figure that the transmittance of the glass-ceramics decreases gradually with the increase of ZnO content. The average transmittance of samples Z0 and Z2 with a thickness of 2 mm in the visible range is 83% and 69%, respectively, which indicates that both of them exhibit excellent transparency and can be used in the area of lasers or optical amplifiers. It is notable that the crystallinity of sample Z2 is up to 92%, which is much higher than that of the traditional transparent glass-ceramics containing small to moderate crystallized volume fraction. However, as the secondary phase pyrope forms and grows in the glass matrix at higher ZnO content, the sample Z4 turns to be slightly translucent and the sample Z5 opacifies completely. The small difference between the refractive index of the glass matrix and crystal phase is one main factor which must be considered to obtain transparent glass-ceramics, and this factor prevails, regardless of crystal size [26]. The refractive index of α-cordierite crystal is 1.524 in our glass-ceramics, while that of the four parent glasses are 1.546, 1.549, 1.554 and 1.557 with the increase of ZnO content, respectively. Thus, the difference of refractive index between crystal phase and matrix glass increases gradually, which can cause a great decrease of transmittance. Besides, the appearance of the secondary phase pyrope results in a significant drop in transmittance of glass-ceramics as it has a higher value of refractive index (1.74) compared with α-cordierite. Moreover, the transmittance of glass-ceramics decreases with the enhancement of crystallinity. Thus, the transmittance of the glass-ceramics decreases gradually with ZnO addition.

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to affect the various properties of the obtained glass-ceramics. In this investigation, we measured density, thermal expansion coefficient, Vickers hardness and bending strength of the glass-ceramics. In general, the density increases with the increase of ZnO content, which is shown in Fig. 7. The density of the corresponded sample increase greatly when the content of ZnO increases to 5 mol%, this phenomenon may result from the formation of a large amount of pyrope which has higher density (3.62 g/cm3) than α-cordierite (2.46 g/cm3). However, it is notable that the density of glass-ceramics is lower than that of their parent glass, which has been proven in the previous investigation [27] as there was an increase in volume during the process of phase transformation. As the type and content of crystal phases are different in these four samples, their thermal expansion coefficients are bound to be different, which is shown in Fig. 7, presenting in shape of parabola with a minimum. Only the α-cordierite, μ-cordierite and pyrope formed in the glass matrix, and their thermal expansion coefficients are 1.4 × 10 − 6 °C − 1 , 2.3 × 10 − 6 °C − 1 and 27 × 10 − 6 °C − 1. It is valid that the expansion coefficient initially decreases due to the enhancement of α-cordierite and afterwards increases greatly for the formation of pyrope. Hardness and bending strength are the two important basic characteristics of materials. Fig. 8 displays the Vickers hardness and bending strength of the glass-ceramics against ZnO content after being crystallized at 1000 °C for 6 h. The hardness changes with the content of ZnO, and this phenomenon can be understood on the basic of XRD result as explained above. The glass network becomes more rigid during phase transformation as the α-cordierite has higher bond strength than μ-cordierite, which may contribute to the enhancement of hardness. However, the precipitation of pyrope hinders the formation of α-cordierite by degree and decreases the hardness. On the other hand, replacement of B2O3 by ZnO also changes the bending strength of the glass-ceramics, and this tendency is related to the change in crystallinity. Based on the analysis of Fig. 4, the crystallinity of four glass-ceramics are 56%, 92%, 85%, and 87%, but the sample Z5 appears to have spontaneous microcracks for the formation of a large amount of pyrope, so it is reasonable to see that tendency. 4. Conclusions

3.6. Thermal and physical properties of the glass-ceramics According to the former analysis, the introduction of ZnO influence the crystallization behavior of the glass-ceramics, thus it is reasonable

Fig. 6. Transmittance spectra and photographs of samples containing different ZnO contents crystallized at 1000 °C for 6 h: (a) Z0; (b) Z2; and (c) Z4.

Transparent cordierite-based glass-ceramics with high crystallinity were prepared by the controlled crystallization of parent glass with different ZnO additions. As the B2O3 is replaced by ZnO gradually, the glass transition temperature changed slightly, while the onset crystallization temperature and the crystallization peak temperatures shifted to lower values. Experiments demonstrated that the addition of ZnO promoted the transformation from μ-cordierite into α-cordierite, as well as

Fig. 7. Density and TEC of the glass-ceramics containing various ZnO contents after being crystallized at 1000 °C for 6 h.

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Fig. 8. Vickers hardness and bending strength of the glass-ceramics against ZnO content after being crystallized at 1000 °C for 6 h.

enhanced the crystallinity and changed the grain size. However, as the ZnO content increased to 4 mol%, the pyrope appeared and affected the various properties of the glass-ceramics greatly. The visible transmittance decreased gradually with the increase of ZnO content. Besides, the thermal expansion coefficient initially decreased and afterwards increased greatly, while the hardness and bending strength showed an inverse trend. In conclusion, ZnO has a great effect on the preparation and properties of transparent cordierite-based glass-ceramics which may be used in the area of lasers or optical amplifiers. Acknowledgments This work has been supported by the National Nature Science Foundation of China (No. 51172286). References [1] A.S. Gouveia-Neto, E.B. da Costa, L.A. Bueno, S.J.L. Ribeiro, Intense red upconversion emission in infrared excited holmium-doped PbGeO3–PbF2–CdF2 transparent glass ceramic, J. Lumin. 110 (2004) 79–84. [2] J. Fu, J.M. Parker, P.S. Flower, R.M. Brown, Eu3+ ions and CaF2-containing transparent glass-ceramics, Mater. Res. Bull. 37 (2002) 1843–1849. [3] X. Qiao, X. Fan, M. Wang, Luminescence behavior of Er3+ in glass-ceramics containing CaF2 nanocrystals, Scr. Mater. 55 (2006) 211–214.

[4] A.X. Lu, Highly crystalline transparent glass ceramics: a challenging important research direction, Comments Inorg. Chem. 32 (2011) 277–288. [5] T. Berthier, V.M. Fokin, E.D. Zanotto, New large grain, highly crystalline, transparent glass-ceramics, J. Non-Cryst. Solids 354 (2007) 1721–1730. [6] S.H. Knickerbocker, A.H. Kumar, L.M. Kumar, L.M. Herron, Cordierite glass-ceramics for multilayer ceramic packaging, Am. Ceram. Soc. Bull. 72 (1993) 90–95. [7] R. Chaim, V. Talanker, Microstructure and mechanical properties of SiC/cordierite glass-ceramic composites, J. Am. Ceram. Soc. 78 (1995) 166–172. [8] J. Banjuraliza, H. Moharmad, Z.A. Ahmad, Synthesis and characterization of xMgO– 1.5Al2O3–5SiO2 (x = 2.6–3.0) system using mainly talc and kaolin through the glass route, Mater. Chem. Phys. 129 (2011) 910–918. [9] X.J. Hao, X.L. Hu, Z.W. Luo, A.X. Lu, Preparation and properties of transparent cordierite-based glass-ceramics with high crystallinity, Ceram. Int. 41 (2015) 14130–14136. [10] R. Muller, E.D. Zanotto, V.M. Fokin, Surface crystallization of silicate glasses: nucleation sites and kinetics, J. Non-Cryst. Solids 274 (2000) 208–231. [11] S.P. Hwang, J.M. Wu, Effect of composition on microstructural development in MgO–Al2O3–SiO2 glass-ceramics, J. Am. Ceram. Soc. 84 (2001) 1108–1112. [12] M.C. Glendenning, W.E. Lee, Microstructural development on crystallizing hotpresses pellets of cordierite melt-derived glass containing B2O3 and P2O5, J. Am. Ceram. Soc. 79 (1996) 705–713. [13] S.H. Knickerbocker, A.H. Kumar, L.W. Herron, Cordierite glass-ceramics for multilayer ceramic packaging, Am. Ceram. Soc. Bull. 72 (1993) 90–95. [14] Y. Demirci, E. Günay, Crystallization behavior and properties of cordierite glassceramics with added boron oxide, J. Ceram. Process. Res. 12 (2011) 352–356. [15] J.M. Wu, S.P. Hwang, Effect of (B2O3, P2O5) additives on microstructural development and phase transformation kinetics of stoichiometric cordierite glass, J. Am. Ceram. Soc. 83 (2000) 1259–1265. [16] G.H. Chen, Effect of ZnO addition on properties of cordierite-based glass-ceramics, J. Mater. Sci. Mater. Electron. 18 (2007) 1253–1257. [17] B. Mirhadi, B. Mehdikhani, N. Askari, Effect of zinc oxide on microhardness and sintering behavior of MgO–Al2O3–SiO2 glass-ceramic system, Solid State Sci. 14 (2012) 430–434. [18] G.H. Chen, X.Y. Liu, Sintering, crystallization and properties of MgO–Al2O3–SiO2 system glass-ceramics containing ZnO, J. Alloys Compd. 431 (2007) 282–286. [19] A. Hrüby, Evaluation of glass-forming tendency by means of DTA, Czechoslov. J. Phys. 22 (1972) 1187–1193. [20] S.N. Salama, S.M. Salama, H. Darwish, The effect of nucleation catalysts on crystallization characteristics of aluminosilicate glasses, Ceramics-Silikáty 46 (2002) 15–23. [21] P. Tarte, Infra-red spectra of inorganic aluminates and characteristic vibrational frequencies of AlO4 tetrahedra and AlO6 octahedra, Spectrochim. Acta 23 (1967) 2127–2143. [22] B.J. Saikia, G. Parthasarathy, Fourier transform infrared spectroscopic characterization of kaolinite from Assam and Meghalaya, northeastern India, J. Mod. Phys. 1 (2010) 206–210. [23] C. Huang, E.C. Behrmsn, Structure and properties of calcium aluminosilicate glasses, J. Non-Cryst. Solids 128 (1991) 210–321. [24] E.I. Kamitsos, M.A. Karakassides, A vibrational study of lithium borate glasses with high Li2O content, Glass Phys. Chem. 28 (1987) 203–205. [25] W.W. Shaver, S.D. Stookey, Pyroceram, SAE Tech. Pap. 66 (1959) 29–36. [26] G.H. Beall, D.A. Duke, Transparent glass-ceramics, J. Mater. Sci. 4 (1969) 340–352. [27] M.D. Krkhanavala, F.A. Hummel, The polymorphism of cordierite, J. Am. Ceram. Soc. 12 (1953) 389–392.