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Influence of amorphous phase separation on the crystallization behavior of glass-ceramics in the BaO-TiO 2 -SiO 2 system Emilie Boulay, Cline Ragoen, Stphane Godet ULB, 4MAT Department, CP194/3, 87 Av. Buyl, 1050 Brussels, Belgium Crystallization 2012 Goslar, Germany 25 th September 2012

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APS role BaO-TiO 2 -SiO 2 Results & Discussions Conclusions Perspectives Outline Influence of phase separation on crystallization Motivations The BaO-TiO 2 -SiO 2 system Results & Discussion Conclusions Perspectives 2 Crystallization 2012 - Goslar

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APS role BaO-TiO 2 -SiO 2 Results & Discussions Conclusions Perspectives Amorphous phase separation (APS) Well known in glass systems APS = matrix + droplets due to liquid immiscibility 3 APS role Crystallization 2012 - Goslar

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APS role BaO-TiO 2 -SiO 2 Results & Discussions Conclusions Perspectives Amorphous phase separation (APS) Well known in glass systems APS = matrix + droplets due to liquid immiscibility Shift in composition + creation of interfaces 4 Interfaces In the droplets In the matrix APS role Shift I. Gutzow, J. Schmelzer, The vitrous state: thermodynamics, structures, rheology and crystallization, Springer, 1995 Crystallization 2012 - Goslar

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APS role BaO-TiO 2 -SiO 2 Results & Discussions Conclusions Perspectives Possible effects of APS on crystallization [1] Scherrer, G W et Uhlmann, D R., 1976[8] ] Harper, H et McMillan, P W., 1972 [2] Hammel, J J., 1966[9] Bhattacharyya, S, et al., 2009 [3] Boulay, 2011[10] Tomozawa, M, et al., 1990 [4] K. Nakagawa, T. Izumitani, 1969[11] Hijiya, H et al., 2008 [5] James, P F et Ramsden, A H., 1984[12] Li Z., 1985 [6] Katsumata, K, et al., 2004 [7] Jiazhi, L et Chih-yao, F., 1986 5 No influenceShift matrixShift dropletsInterfaces -Interfacial Energy -Diffusion zone Na2O-SiO2 [1]BaO-SiO2 [5]LaF3-Na2O-Al2O3-SiO2 [9]Li2O-SiO2 [10] Na2O-CaO-SiO2 [2][3]TiO2-SiO2 [6]BaO-SiO2-TiO2 [11] Li2O-SiO2 [4]MgO-Al2O3-SiO2-TiO2 [7] ZnO-Al2O3-SiO2 [7] ZnO-Al2O3-SiO2-ZrO2 [7] Interfaces do not promote crystallization [3] [4] [12] Li2O-SiO2-P2O5 [8] APS role Crystallization 2012 - Goslar

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APS role BaO-TiO 2 -SiO 2 Results & Discussions Conclusions Perspectives Possible effects of APS on crystallization 5 No influenceShift matrixShift dropletsInterfaces -Interfacial Energy -Diffusion zone Na2O-SiO2 [1]BaO-SiO2 [5]LaF3-Na2O-Al2O3-SiO2 [9]Li2O-SiO2 [10] Na2O-CaO-SiO2 [2][3]TiO2-SiO2 [6]BaO-SiO2-TiO2 [11] Li2O-SiO2 [4]MgO-Al2O3-SiO2-TiO2 [7] ZnO-Al2O3-SiO2 [7] ZnO-Al2O3-SiO2-ZrO2 [7] Interfaces do not promote crystallization [3] [4] [12] Li2O-SiO2-P2O5 [8] APS role Systematic study of prior amorphous phase separation effect on crystallization in the BaO-TiO2-SiO2 system: -Interfaces: debated in literature -Photoluminescence properties Crystallization 2012 - Goslar

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APS role BaO-TiO 2 -SiO 2 Results & Discussions Conclusions Perspectives The BaO-TiO 2 -SiO 2 system This glass system exhibits APS by the presence of a large miscibility gap in the silica corner The exact miscibility gap location is unknown Crystal phase near immiscibility: fresnoite (2BaO.TiO 2.2SiO 2 ) * Hijiya et al., Effect of phase separation on crystallization of glasses in the BaO-TiO 2 -SiO 2 system, 2009 ? BaO-TiO 2 -SiO 2 Crystallization 2012 - Goslar 6

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APS role BaO-TiO 2 -SiO 2 Results & Discussions Conclusions Perspectives Technical interests of fresnoite Fresnoite exhibits blue/white photoluminescence (PL) under ultraviolet excitation PL effect can be optimized by heat treatments on the stoichiometric composition Photoluminescence T. Komatsu, Effect of heat treatment temperature on the optical properties of Ba 2 TiSi 2 O 8 nanocrystallized glasses, 2005 Excitation at 254 nm Response at 470 nm 7 BaO-TiO 2 -SiO 2 Crystallization 2012 - Goslar

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APS role BaO-TiO 2 -SiO 2 Results & Discussions Conclusions Perspectives Possible enhancement of optical properties No stoichiometric compositions show also PL effect ( =254 nm) Hijiya (2008) suggested phase separation may have an influence on crystallization and PL effect Hijiya et al., Effect of phase separation on crystallization of glasses in the BaO-TiO 2 -SiO 2 system, 2009 Stoich. Non stoich. APS [211] intensity vs [002]: orientation PL effect 8 SiO 2 BaO-TiO 2 -SiO 2

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APS role BaO-TiO 2 -SiO 2 Results & Discussions Conclusions Perspectives Material investigated Fresnoite-SiO 2 line Quenched after melting FRES NoAPS APS 9 Quenched after melting FRES: stoichiometric composition NoAPS: non stoichiometric composition outside the miscibility gap APS: non stoichiometric composition inside the miscibility gap Mixing powder + melting (1500-1560C, 3H) Air quenched + annealed (600C, 10H) Water-quenched after melting Crystallization 2012 - Goslar Results & Discussions

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APS role BaO-TiO 2 -SiO 2 Results & Discussions Conclusions Perspectives Crystallization mechanism by DSC Effect of quenching rate Effect of composition Microstructure by SEM Morphologies at early and final stages of crystallization Morphological orientation: Large scale: XRD Small scale: EBSD (FEG SEM) and ACOM (TEM) Crystallization 2012 - Goslar 10 Results & Discussions

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APS role BaO-TiO 2 -SiO 2 Results & Discussions Conclusions Perspectives APS air-quenched versus APS water-quenched No prior APS (APS) 11 Prior APS (APS) Crystallization 2012 - Goslar Results & Discussions

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APS role BaO-TiO 2 -SiO 2 Results & Discussions Conclusions Perspectives FRES Cristallization mechanism Effect of composition APS 12 112