Electrical characterization of polycrystalline sodium β″-alumina: Revisited and resolved

•AC 4-probe method with Au electrode was successfully applied to SBA polycrystals.•AC 4-probe and 2-probe methods are rigorously compared.•Bulk dispersion due to mobile charge carriers are modeled by the Cole–Davidson function.•Current-constriction effects are described by the Cole–Davidson dielectric function.•Ideal Warburg response is present regardless of the electrode condition.

AC 4-probe method using Au electrodes distinguished the sample conductivity of polycrystalline β″ alumina at high temperature. Bode plots of AC 2-probe measurements revealed temperature-independent capacitance plateaus and the power-law frequency dependences, which can be described by Cole-Davidson dielectric equations. The relaxation time constants exhibit the same activation energy as the bulk conduction supporting CK1 model and current-constriction mechanism. An ideal Warburg response is identified regardless of the electrode condition. Well-defined parameters allow the simulation of AC behavior as a function of temperature as well as frequencies, which provides much informative overview of the AC characteristics of solid electrolytes.