HIGH-TEMPERATURE AC ELECTRICAL BEHAVIOR OF POLYCRYSTALLINE CALCIUM ZIRCONATE

The a.c. electrical response of undoped polycrystalline calcium zircon ate was evaluated at elevated temperatures (900 less than or equal to T less than or equal to 1400 degrees C) in air as a function of freque ncy in the range 5 Hz to 13 MHz. A systematic analysis of the a.c. ele ctrical data revealed semicircular relaxation(s) in the impedance, adm ittance and modulus planes. An equivalent circuit model, representing grain and grain-boundary regions, is proposed. This circuit can be tra nsformed to another representation which incorporates a possible trapp ing effect across the grain boundaries. The equivalence of these two r epresentations is demonstrated by examining the correspondence between the two sets of circuit elements without resorting to empirical distr ibuted-element models.