Phase diagram and properties of Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 polycrystalline ceramics

yPb(In1/2Nb1/2)O3–(1 − x − y)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (yPIN–(1 − x − y)PMN–xPT) polycrystalline ceramics with morphotropic phase boundary (MPB) compositions were synthesized using columbite precursor method. X-ray diffraction results indicated that the MPB of PIN–PMN–PT was located around PT = 0.33–0.36, confirmed by their respective dielectric, piezoelectric and electromechanical properties. The optimum properties were found for the MPB composition 0.36PIN–0.30PMN–0.34PT, with dielectric permittivity ɛr of 2970, piezoelectric coefficient d33 of 450 pC/N, planar electromechanical coupling kp of 49%, remanent polarization Pr of 31.6 μC/cm2 and TC of 245 °C. According to the results of dielectric and pyroelectric measurements, the Curie temperature TC and rhombohedral to tetragonal phase transition temperature TR–T were obtained, and the “flat” MPB for PIN–PMN–PT was achieved, indicating that the strongly curved MPB in PMN–PT system was improved by adding PIN component, offering the possibility to grow single crystals with high electromechanical properties and expanded temperature usage range (limited by TR–T).