Dielectric Relaxations in the Ca-Doped CeO₂ System

Abstract

Dielectric relaxations were investigated for 10 mol% Ca-doped CeO₂ (Ce_0.9Ca_0.1O_2-δ) having a cubic fluorite-type structure, which is a typical oxide-ion conductor. The dielectric constants (ε_r′) showed anomalously large values at low frequencies and high temperatures. Numerical analysis of the frequency dependence of ε_r′ clarified that the large ε_r′ originated from superimposition of both the electrolyte-electrode interfacial and Debye-type polarizations. The ac conduction dispersion was also successfully explained by the interfacial and Debye-type polarizations. Two kinds of Debye-type relaxations observed were ascribed to defect associates, (Ca_Ce″-V_O^••) which have different distances between the dopant and the oxygen vacancy.