Domain switching and microcracking during poling of lead zirconate titanate ceramics

Abstract

The application of a DC electric field (poling) to a ferroelectric lead zirconate titanate (PZT) ceramic aligns domains in the field direction. The non 180°-domain switches involve mechanical deformations, which are detected as acoustic emission signals. Concurrent with AE signals, electrical current pulses arise from domain reorientations. When the poling field is large and domain switches are extensive, the resulting deformations, under the constraint of neighboring domains or grains, may exceed the elastic limit and cause microcracking. The onset and propagation of microcracking during poling of PZT is signalled by the appearance of continuous AE signals, unaccompanied by current pulses, in contrast to intermittent AE signals accompanied by corresponding current pulses during domain switching. The onset and extent of microcracking established by this method is confirmed by scanning electron micrographs and decrease in the value of piezoelectric coefficient (d₃₃) and mechanical quality factor (Q_M). The amplitude of AE signals due to domain switches are spread widely, while that of AE signals caused by microcracking occur in a narrow range around 50 db.