Effects of Pressure on Piezoelectric and Dielectric Responses of Relaxor Ferroelectric Solid Solution Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ Binary System Ceramics near a Morphotropic Phase Boundary Composition

Abstract

The piezoelectric and dielectric properties of Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMNT) ceramics with compositions near a morphotropic phase boundary (MPB) were investigated under pressures p up to 700 MPa at 25 °C. The resonance and antiresonance frequency characteristics of impedance and phase in the k31 mode for PMNT (67/33) and (69/31) ceramics were observed under various pressures. The effect of pressure on their responses were clearly observed. The electromechanical coupling coefficient k31 in the k31 mode increases and the electromechanical quality factor Q decreases with increasing p at pressures lower than 100 MPa. The decrease in Q with p is due to the scattering of ultrasonic waves from the domain boundary. The relative permittivity εr increases with increasing p. Such increases in both k and εr with p seem to be related to the increase in topographical domain-wall density associated with monoclinic distortions. At pressures higher than 100 MPa, their electromechanical suppression in PMNT ceramics occurs at each pressure, corresponding to the electromechanical coupling coefficient k. εr increases with pressure-induced electromechanical suppression. The change in εr with such suppression corresponds to k. Such a phenomenon seems to be due to the increase in piezoelectric load based on the increase in complex domain wall density coming from the increase in free energy with pressure.