TRANSPORT PROPERTIES OF THE MIXED-CONDUCTIVITY COMPOUND AG1.92TE AT 160-DEGREES-C

摘要

The transport properties of the mixed-conductivity compound Ag1.92Te have been investigated within its homogeneity range at a temperature of 160 degrees C. The composition dependence of the chemical diffusion coefficient has been obtained from galvanostatic polarization experiments on the asymmetric cell AgAgIAg1.92TePt employing coulometric titrations for composition variation. Evaluation formulas for mixed conductors with arbitrary electronic transport numbers permit the determination of the chemical diffusion coefficient of Ag1.92Te. The electronic transport numbers needed for the calculations have been obtained from separate measurements of the partial conductivities. The chemical diffusion coefficient decreases slightly with decreasing silver content with typical values around 0.004 cm(2) s(-1). The electronic conductivity increases with decreasing silver content with values in the range of 4-10 S cm(-1), while the ionic conductivity is independent of silver activity, with typical values around 0.9 S cm(-1). The electronic properties have been interpreted in terms of a simple model considering nondegenerate electrons and nondegenerate holes. (C) 1997 Academic Press. [References: 30]