Phase structures and electrical properties of Sm doped PSN-PMN-PT ceramics

•The crystal structure, electrical properties and thermal stability were investigated for Sm-PSN-PMN-xPT ceramics.•The excellent electric properties were achieved: d33 ~ 815 pC/N and Tm ~135 °C.•These high properties are mainly resulted from intrinsic contributions.•d33 and kp achieved insensitive temperature-dependent behavior from 30 °C to 110 °C. A series of 2 mol% Sm doped 0.15Pb(Sc1/2Nb1/2)O3-(0.85-x)Pb(Mg1/3Nb2/3) O3-xPbTiO3 (Sm-PSN-PMN-xPT, x = 0.32, 0.33, 0.35 and 0.37) piezoelectric ceramics were fabricated by solid-state method, and the detailed crystal structure, electrical properties and thermal stability were investigated. The Rietveld fitting XRD results show the ceramics with x = 0.32 and 0.33 possess concomitant monoclinic (Mc) and rhombohedral (R) phases at room temperature, while coexistence phases of tetragonal (T) and monoclinic (Mc) are observed in x = 0.35 and 0.37 ceramics. The high piezoelectric coefficient d33 of 815 pC/N and electromechanical coupling coefficient kp of 0.61, and a large unipolar strain Smax of 0.134% accompanied by a small strain hysteresis of 4.74% are obtained in x = 0.33 ceramics. Through the Rayleigh analysis, these high properties are mainly derived from intrinsic contributions (lattice distortion and reversible domain walls displacement). It is particularly important that in the temperature range from 30 °C to 110 °C, the variations of d33 and kp are only 8% and 13%, respectively, demonstrating insensitive temperature-dependent behavior of x = 0.33 ceramics, which can be further confirmed by the temperature dependence of εr × Pr, showing a variation of less than 14%. Our results indicated the Sm doped PSN-PMN-PT ceramics have potential applications in high performance medical ultrasonic imaging transducers and actuators.