Electrochemical Determination of the Activity of Na2O in the Pyrochlore Phase of the Sb2O4‐NaSbO3 System

Abstract
Activity of Na2O in the pyrochlore phase of the system Sb2O4‐NaSbO3 has been measured as a function of temperature in the range 1073–1412 K by electromotive force (emf) measurements of the following solid‐state electrochemical cells: image The solid electrolyte used in the above electrochemical cells is Na‐ß‐Al2O3, which is an excellent sodium‐ion conductor in the temperature range of the measurements. From the measured reversible emf, the activity of Na2O in the Sb2O4‐NaSbO3 system has been calculated. The temperature dependence of the logarithm of the activity of Na2O in various two‐phase regions of the Sb2O4‐NaSbO3 system can be represented as image No thermodynamic data have been reported earlier in the literature for the system Sb2O4‐NaSbO3, and the present data constitute the first thermodynamic information.