Relationship between oxide-ion conductivity and dielectric relaxation in Sm-doped CeO2

The relationship between electrical conduction and dielectric relaxation was investigated for 20 at.% Sm doped CeO2 (Ce0.8Sm0.2O2−δ), which is a typical oxide-ion conductor. Numerical calculation clarified that the anomalously large dielectric constant (εr′) originated from the superimposition of both Debye-type polarization and interfacial polarization between electrolyte and electrode. Two kinds of the Debye-type relaxation appeared at and above 673 K, which were assigned to defect associates, (SmCe′–VO) and (SmCe′–VO–SmCe′)x. The Debye-type polarization was also confirmed by analyzing the dielectric loss factor (εrʺ). Ac conductivity (σac) in high temperature and high frequency regions agreed with dc conductivity (σdc), while the dispersion of σac was ascribed to the Debye-type polarizations.