Anomalies of the dielectric and electromechanical responses of multicomponent ceramics on the basis of PMN–PT near the morphotropic phase boundary

The dielectric and electromechanical responses of ceramics m PbMg 1/3 Nb 2/3 O 3 – n PbNi 1/3 Nb 2/3 O 3 – y PbZn 1/3 Nb 2/3 O 3 – x PbTiO 3 ( m  = 0.1298–0.4844, n  = 0.1266–0.4326, y  = 0.0842–0.130, x  = 0.25–0.40) compositions near the morphotropic phase boundary have been studied. The evolution of the dielectric constant and the longitudinal strain dependences of studied ceramics on an electric field with increasing content x from those typical for relaxor ferroelectrics to those typical for classic ferroelectrics is observed. The occurrence of plateau-like anomalies in the dependences of the dielectric constant and the longitudinal strain of heterophase ceramics ( x  ≈ 0.30–0.35) on the electric field has been established. It has been revealed that the reason for the observed anomalies in the bipolar regime on the application of an electric field is termination of non-180°-domain switching due to high mechanical stresses caused by induced phase transition of the heterophase (tetragonal and pseudocubic) into single-phase (tetragonal) state. It is found that there are no plateau-like anomalies in the unipolar regime of electric field changes. It is shown that ceramics with x  = 0.275 have high performance ( d 33  = 1600 pm/V at E  = 4 kV/cm) for application in actuators and tunable devices.