The AC Electrical Behavior of Hydrothermally Synthesized Barium Titanate Ceramics

Abstract

The ac electrical response of hydrothermally synthesized polycrystalline barium titanate ( BaTiO 3 ) was studied as a function of frequency using immittance measurements at temperatures ranging from 200 to 500° C in air. Two semicircular relaxations were observed in impedance ( Z * ) and modulus ( M * ) planes. The capacitance of the high-frequency relaxation obtained from these complex planes showed a Curie-Weiss behavior originating from a lumped grain contribution. The low-frequency relaxation exhibited a high capacitance which was invariant with temperature, suggesting a possible grain-boundary contribution. The grain-boundary resistance was found to be higher than that of grains at all temperatures. An equivalent circuit consisting of two parallel R C combination in series is evident from the Z * - and M * -plane analyses, and represents the individual contribution of grain and grain-boundary regions of the polycrystalline sample. Another circuit consisting of a series R C combination in parallel with a dc resistance ( R 0 ) and a high-frequency limit capacitance ( C ∞ ) is identified. This circuit portrays a possible trapping effect revealed by the admittance ( Y * ) and capacitance ( C * ) plane analyses. The two circuits are equivalent and complementary to each other as they together provide more information on the operative electrical processes in the sample.