Electrode Effects on Dielectric Relaxation in Oxide-Ion Conductor Ce0.7Yb0.3O2-\delta Having a Fluorite-Type Structure

The frequency dependences of the dielectric constant ($\varepsilon_{\text{r}}$$'$) for the oxide-ion conductor Ce 0.7 Yb 0.3 O 2-\delta with two types of electrode, Pt and La 0.6 Sr 0.4 FeO 3-\delta (LSF), were successfully explained by the superposition of polarizations due to charging currents and Debye-type dipoles of the dopant--vacancy associates, [Yb \text{Ce $'$--V \text{O ** ] * and [Yb \text{Ce $'$--V \text{O ** --Yb \text{Ce $'$] \times . The magnitudes of polarizations of the associates were very large for the sample with the Pt electrode, but were smaller by one or two orders of magnitude for the sample with the LSF electrode. The bulk and grain-boundary resistivities in the impedance spectra of Ce 0.7 Yb 0.3 O 2-\delta , which ought to be invariable regardless of the type of electrode used, showed a large difference between the samples with Pt and LSF electrodes. As a result, the impedance spectra were also explained by the Debye-type dipoles of the dopant--vacancy associates.