Phase equilibria and thermodynamic properties of components in the Cs2O-B2O3-SiO2 system at high temperatures

The phase equilibria in the Cs^sub 2^O-B^sub 2^O^sub 3^-SiO^sub 2^ system are investigated in the temperature range 873-1073 K by the annealing-quenching technique, high-temperature microscopy, and X-ray powder diffraction analysis. The vapor composition, the activities of the components, and the Gibbs energies of glasses and melts in the Cs^sub 2^O-B^sub 2^O^sub 3^-SiO^sub 2^ system are determined at a temperature of 1020 K. It is demonstrated that glasses and melts in the Cs^sub 2^O · B^sub 2^O^sub 3^-Cs^sub 2^O · SiO^sub 2^ system are characterized by positive deviations of the CsBO^sub 2^ activities and negative deviations of the Cs^sub 2^O · SiO^sub 2^ activities from ideal behavior. As a consequence, the deviations of the Gibbs energies from ideal behavior change their sign.[PUBLICATION ABSTRACT]