Effects of ZnO on the stability of the SiO2-BaO-TiO2 system

Abstract Glasses in the SiO 2 -BaO-TiO 2 system are known to exhibit high refractive indices and exceptional infrared transmission. However, their strong tendency towards crystallization limits their production and commercial applications. In this study, we substituted ZnO for SiO 2 , BaO and TiO 2 , respectively, in a baseline 20SiO 2 -30BaO-50TiO 2 glass. These glasses were synthesized by a traditional melt-quench method. The crystalline nature of both quenched between two metallic plates and heat-treated samples were assessed using X-ray diffraction (XRD) analysis, while differential scanning calorimetry (DSC) was used to estimate △T (T x -T g ), K gl , activation energy (E a ), and the Avrami parameter (n). The structure of the SiO 2 -BaO-TiO 2 -ZnO glass system was characterized by Raman spectroscopy, while SEM was performed for microstructural characterization of glassy and crystalline phases. The results indicate that these glasses can incorporate between 10 and 20 mol% of ZnO before crystallization occurs, where the maximum ZnO concentration is highly dependent upon the oxide substitution method. The apparent activation energy (E a ) of 20SiO 2 -30BaO-50TiO 2 and Zn-Ba-2.5 are 796 kJ/mol and 511 kJ/mol while Avrami parameters (n) are 2.02 and 3.04, respectively. SEM analysis demonstrates that both glasses undergo volume crystallization. Comparing with 20SiO 2 -30BaO-50TiO 2 glass, ZnO promotes the formation of [TiO 4 ] and “supertetrahedra” structures which can increase △T and K gl to 110 °C and 0.30 respectively. ZnO additions to the SiO 2 -BaO-TiO 2 glass system improves glass stability against crystallization.