Electrochemical properties of Cs-substituted CaWO4 and BaWO4 oxide ion conductors

Abstract

High-temperature electrochemical properties of Cs-substituted CaWO4 and BaWO4 have been investigated. When cesium ions are partly substituted for calcium site of Scheelite-type structured CaWO4 to form oxide ion vacancies as Ca1-xCsxWO4-x/2, oxide ion conduction appears at elevated temperatures. This defect structure for the oxide ion conduction is in contrast to the PbWO4-based oxide ion conductor with oxide ion interstitials, Pb1-xLaxWO4+x/2. The measured electric conductivity of Ca1-xCsxWO4-x/2 (x = 0.15) is high as 10-2 Scm-1 at 750°C with the oxide ion transport number relatively close to unity. Essentially the similar results are obtained for the barium analogous system Ba1-xCsxWO4-x/2, although the conductivity is still lower than CaWO4-based system.