Aging and the Double Hysteresis Loop of PbλCa1‐λTiO3 Ceramics

Abstract

Double hysteresis loops were observed in a solid solution, Pb0.5Ca0.5TiO3, which was held at room temperature for several hours after cooling from a high temperature (200°C.). To discover the mechanism of the processes causing the peculiar hysteresis loops, the loops and the dielectric properties were examined under various conditions. It was found that specimens of the foregoing composition exhibit a remarkable aging effect at room temperature. The double hysteresis loop is explained as follows. Each small region in the specimen has an asymmetric hysteresis loop. The observed propeller‐shaped hysteresis loop is the result of random superpositions of all these asymmetric hysteresis loops. Experimental results show that the asymmetry of the elemental hysteresis loop originates in an interaction between two phases which are formed as the aging proceeds. A phenomenological theory is developed in which the effects of the mutual interactions between the two phases are considered. This interaction causes the elemental hysteresis loops to be asymmetric. The theory succeeds, at least qualitatively, in explaining the main features of the observed facts.