Dielectric relaxations in the Ce1−xNdxO2−δ system

Dielectric relaxations were investigated for the solid solution system Ce1−xNdxO2−δ (0.0 ≦ x ≦ 0.5) having a fluorite-type structure, which is a typical oxide-ion conductor. The dielectric constants showed anomalously large values at low frequencies and high temperatures. Numerical analysis of frequency dependence of dielectric constant (εr′) clarified that the anomalously large εr′ originated from the superimposition of both Debye-type polarization and interfacial polarization between electrolyte and electrode. Two kinds of Debye-type relaxations observed were ascribed to defect associates, (NdCe′ − VO¨)· and (NdCe′ − VO¨ − NdCe′)x. The Debye-type polarizations were also confirmed by analyzing the dielectric loss factor (εr″). When the oxide-ion conductivity decreased in the heavy Nd-doped samples, both the Debye-type and the interfacial polarizations also decreased, suggesting that ordering of oxygen vacancy suppressed the electric field response of Debye-type polarization, resulting in the decrease of oxide-ion conductivity.