Ceramics-Silikáty 36, (1) 1 - 6 (1992)

A study of the thermodynamic properties of the Na₂O - SiO₂ binary melt by means of a concentration cell with conversion made use of the oxygen probe with solid ZrO₂ electrolyte stabilized with Y₂O₃ as the reversible electrode. The partial molar values ΔG(Na₂O), ΔHG(Na₂O) a ΔS(Na₂O) were determined from the temperature dependence of emf with respect to the reference melt 0.40 (Na₂O) - 0.60 (SiO₂). The values of partial molar enthalpy and entropy show a distinct minimum in the region of 50 molar % of SiO₂, which is indicative of stability of the Na₂SiO₃ compound. On the basis of measuring the partial pressure of oxygen in the Na₂O - SiO₂ melt, a contribution of electron conductivity of the solid electrolyte was established only with the basic system at a high Na₂O content. The error due to electron conductivity of the solid electrolyte was proved to have no effect on the emf value of the concentration cell in view of the experimental error involved in the application of oxygen probes.