AC 4-probe method using Au electrodes distinguished the sample conductivity of polycrystalline beta" 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. (C) 2014 Elsevier B.V. All rights reserved.