低硫黄分圧下におけるCaS-1 wt%Y<SUB>2</SUB>S<SUB>3</SUB>固体電解質の導電率

Abstract

The CaS-1 wt%Y2S3 solid electrolyte has been expected to be effective for thermodynamic studies of metal-sulfide systems. An acceptable solid-sulfide electrolyte must exhibit essentially complete ionic conductivity. The conductivity of the CaS-1 wt%Y2S3 solid solutions was determined by an a.c. bridge measurement-complex impedance plot combination method. Sulphur partial pressures were established by using metal-metal sulfide coexistence electrodes.The isothermal conductivities were constant at a sulphur partial pressures lower than the equilibrium sulphur pressure of Cu-Cu2S coexistence and a gentle fall in conductivity was observed at the Ag-Ag2S equilibrium sulphur pressure. The result suggested that the conductivity of the CaS-1 wt%Y2S3 was ionic with the current carried by the Ca2+ ions via cationic vacancies. However, the conductivity value found in this study, 7.6×10−4 S/m at 1073 K for the CaS-1 wt%Y2S3 solid solution, is much smaller than the order of 10−1 S/m which has been obtained for the ZrO2-CaO, ThO2-Y2S3 and CaF2 solid electrolytes at the same temperature.