Impedance spectroscopy of sulphate solid electrolytes
Abstract Sodium sulphate was doped with yttrium sulphate and sodium phosphate, and the ionic conductivity of these compounds was measured using small signal ac response analysis in a wide frequency range (0.1–65000 Hz). From the composition dependence of the bulk conductivity data of these solid solutions the mobilities of the charge carriers contributing to the conduction have been determined. While both sodium ion vacancies and interstitial sodium ions contribute to the conductivity, the sodium ion vacancies constitute the more mobile species. Secondly, the impedance spectra are fitted with an equivalent circuit description. Diffusion limited electrode processes appear to be important in the materials and ambients examined.