COMPLEX IMPEDANCE ANALYSIS OF UNUSUAL DIELECTRIC-PROPERTIES IN (PB,LA)TIO3 CERAMICS

Both an anomalous broad dielectric peak above the Curie temperature and a normal sharp dielectric peak at the Curie temperature were observed in Pb1-(X)La2X/3 TiO3(X = 0.05-0.20) ceramics. The broad dielectric peak shifted toward higher temperatures with increasing frequency, associated with a decrease in its peak value. The complex impedance loci consisting of two semicircles were found for the materials above the Curie temperature indicating that the dielectric property can be analyzed using an equivalent circuit with a series connection of two RC parallel circuits. The origin of the broad peak has been tentatively interpreted to be an interfacial polarization at the grain boundaries.