Dielectric, piezoelectric, and electromechanical properties of morphotropic phase boundary compositions in the Pb(Mg1/3Ta2/3)O3-PbZrO3-PbTiO3 ternary system

Morphotropic phase boundary (MPB) compositions, separating the rhombohedral and tetragonal phases within the Pb(Mg1/3Ta2/3)O-3-PbZrO3-PbTiO3 (PMT-PZ-PT) ternary system, were identified using x-ray diffraction and confirmed by their dielectric and piezoelectric properties. Optimal properties were found for the MPB composition of 0.4PMT-0.2PZ-0.4PT, with a dielectric constant epsilon(r) and a piezoelectric coefficient (d(33)) of the order of 4000 and 580 pC/N, respectively. The planar and thickness electromechanical coupling factors were found to be k(p)=57.2% and k(t)=44.4%, with a moderate Curie temperature of 175 degrees C. Compositions with increasing PMT content (>0.3) exhibited relaxorlike characteristics, showing dispersive dielectric behavior with respect to frequency, indicative of the decay of the macrodomain state to microdomain state.