Thermal Behavior of Cs2B4SiO9

For the first time, a single-phase sample with a stoichiometry of 1 : 2 : 1 (Cs2B4SiO9) is obtained in the Cs2O–B2O3–SiO2 system using the solid-phase reaction method. It is shown that excess silica leads to stabilization of this phase even under conditions of a deficiency of B and Cs. The thermal behavior up to 950°C is investigated using DSC, TG, and X-ray diffraction, in comparison with the annealing and quenching method. It is shown that Cs2B4SiO9 melts incongruently with the formation of CsBSi2O6. According to dilatometry measurements, the average linear coefficient of thermal expansion (LCTE) of Cs2B4SiO9 in the region up to 400°C is 16 × 10–6°C–1 and 26 × 10–6°C–1 in the temperature range of 450–600°C.