Stabilization of δ-like Bi 2 O 3 Phase at Room Temperature in Binary and Ternary Bismuthate Glass Systems with Al 2 O 3 , SiO 2 , GeO 2 , and B 2 O 3 .

Recently, it was shown that the nanocrystallization of Bi2O3 glasses with the addition of SiO2 and Al2O3 leads to the stabilization of the δ-like Bi2O3 phase at least down to room temperature, which is significantly below its stability range in bulk form. In this research, we investigated the properties of bismuthate glasses synthesized with various glass-forming agents such as SiO2, GeO2, B2O3, and Al2O3. It was demonstrated that vitrification of all these systems is possible using a standard melt quenching route. Furthermore, we investigated the crystallization processes in pristine glasses upon increasing the temperature and the thermal stability of arising phases using thermal analysis and high-temperature XRD in situ experiments. It was shown that it is possible to stabilize crystallites' isostructures with δ-Bi2O3 embedded in a residual glassy matrix down to room temperature. The temperature range of the appearance of the δ-like phase strongly depended on the nominal composition of the glasses. We postulate that the confinement effect depends on the local properties of the residual glassy matrix and its ability to introduce sufficient force to stretch the structure of the δ-like Bi2O3 phase in the nanocrystallites.