1992 Volume 100 Issue 1165 Pages 1172-1174
An investigation has been made on the grain size dependence of the dielectric properties in 0.99Pb0.7La0.2TiO3+0.01MnO2 ceramics exhibiting two anomalous peaks of dielectric constant; One is a sharp peak at the Curie point (-160°C), and the other a broad one above the Curie point. The sharp dielectric constant peak showed no significant change with grain size, while the broad dielectric constant peak significantly increased as the grain size increased. Complex impedance analysis revealed that the dielectric properties of the present materials can well be described using an equivalent circuit with two sets of R-C parallel circuits being connected in series. Evidently, these two R-C parallel circuits give the dielectric properties of the bulk of the grains which provide the sharp dielectric peak and those of the grain boundary region, which yield the broad one, respectively. The origin of the broad dielectric peak is most likely interpreted to be interfacial polarization at the grain boundaries.
