Residual glass and crystalline phases in a barium disilicate glass–ceramic
Investigations about the presence of residual glass are scarce, despite its fundamental role in the crystallization kinetics and luminescent properties of barium disilicate glass–ceramics (BaO·2SiO{sub 2}–BS{sub 2}) with a quasi-stoichiometric composition. Non-isothermal (DTA/DSC) experiments have demonstrated that BS{sub 2} presents a polymorphic transformation, where the h-BS{sub 2} (monoclinic structure) phase is completely transformed in l-BS{sub 2} (orthorhombic structure) at temperatures higher than 1020 °C (10 °C/min). In this study, BS{sub 2} monolithic samples were heat-treated at 1000 °C (BS2-10) and 1100 °C (BS2-11) in a DSC furnace at a heating rate of 10 °C/min. In addition, the crystalline and amorphous phases were characterized and quantified by Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) experiments, respectively. Although the complete polymorphic transformation from h-BS2 to l-BS2 was achieved at 1100 °C, our results demonstrated that BS2-11 contains a minor, albeit not negligible, amount of residual glass. - Highlights: • The crystalline and amorphous phases in a barium disilicate glass were characterized and quantified by XRD and TEM. • The BS2-10 sample was constituted by two main crystalline phases, which consists of 2 polymorphic forms: h-BS2 and l-BS2. • The orthorhombic BS2 phase (l-BS2) was predominant at 1100 °C. • The complete polymorphic transformation from h-BS2 to l-BS2 was achieved at 1100 °C. • Nevertheless, our XRD and TEM results demonstrated that BS2-11 contains a minor amount of residual glass.