Study of the Processes of Non-Stoichiometric Compositions Based on CsSiB₃O₇

In the Cs₂O–B₂O₃–SiO₂ system, samples with different stoichiometric ratios of Cs₂O : B₂O₃ : SiO₂—1 : 3 : 2 (CsSiB₃O₇) and 1.25 : 2.5 : 2—were obtained by solid-phase reactions. The phase formation of cesium borosilicate СsSiB₃O₇ was studied. In samples with a stoichiometric ratio of 1 : 3 : 2, CsSiB₃O₇ crystallizes with impurities of kirchhoffite and CsB₃O₅ at 680°C. At 750°C, melting is observed with the formation of cubic boropollucite CsBSi₂O₆. In samples of nonstoichiometric composition, Cs₂B₄SiO₉ crystallizes at 680°C along with CsB₃O₅. With an increase in temperature to 750°C, only boropollucite is formed.