Mass-Spectrometric Study of Thermodynamic Properties in the RbBO₂-SiO₂ System

Abstract

Partial pressures of RbBO₂ (g) and Rb₂(BO₂)₂ (g) in the RbBO₂-SiO₂ system are measured by a mass-spectrometric Knudsen effusion method. On the basis of the partial pressures, chemical activities of the RbBO₂ and SiO₂ components and molar Gibbs energies of mixing are determined in the whole composition range. The chemical activities of both RbBO₂ and SiO₂ show negative deviation from Raoult's law at 1000 K. From low molar Gibbs energies of mixing, the melts in the RbBO₂-SiO₂ system are concluded to be very stable thermodynamically.