Dielectric and Anelastic Relaxation in Ca‐Doped Cerium Dioxide

Abstract

AbstractMeasurements of dielectric losses and internal friction in Ca‐doped CeO2 have been made over the temperature range 253 to 573 °K on specimens with up to 2.5% of the Ce4+ ions replaced by Ca2+ ions. The observed internal friction and dielectric loss peaks have relaxation times which are in close accord with the predictions of an eight‐position, nearest‐neighbor model, namely, that the relaxation time for electrically‐active modes is equal to twice that for mechanically‐active modes. These relaxations occur because of the redistribution of oxygen vacancies (bound to substitutional Ca2+ ions) among eight sites which are initially equivalent, but which become inequivalent in the presence of the external electric or mechanical stress field. From the temperature dependence of the relaxation times and the peak shape, the activation energy required for such oxygen vacancy jumps is calculated to be 0.86 eV, with the pre‐exponential factor estimated to be 2.4 × 1014 s−1.