Maxwell-Wagner piezoelectric relaxation in ferroelectric heterostructures

Using a serial bilayer model we show that heterogeneous ferroelectric syste ms may exhibit substantial Maxwell-Wagner piezoelectric relaxation. The rel axation has its origin in the coupling of the dielectric and piezoelectric properties. The model predicts both retardation (positive phase angle and c ounterclockwise charge-pressure hysteresis) and relaxation (negative phase angle and clockwise charge-pressure hysteresis) of the longitudinal direct piezoelectric coefficient. The theoretical results are confirmed experiment ally in ferroelectric ceramic-ceramic bilayers and in a single-phase ferroe lectric Aurivillius compound ceramic in which neighboring grains with stron gly anisotropic properties may behave as basic Maxwell-Wagner units. (C) 20 01 American Institute of Physics.