(0.79 - x)Pb(In1/2Nb1/2)O-3-0.21Pb(Zn1/3Nb2/3)O-3-xPbTiO(3) (x = 0.23-0.35) ternary ferroelectric system in the form of ceramics have been synthesized. Its structure and properties have been studied by X-ray powder diffraction and electric measurements. A morphotropic phase boundary region has been determined in the composition range of 0.28 < x < 0.32, where the Curie temperature T-c and the rhombohedral-tetragonal phase transition temperature T-RT were found to vary from 243 C to 295 C and 145 C to 191 C, respectively, much higher than PMNT and PZNT systems. The compositions within MPB region exhibit excellent piezoelectric properties such as piezoelectric coefficient d(33) > 646 pC/N, T-RT > 145 degrees C, T-c > 273 degrees C and E-c > 13 kV/cm for 0.5PIN-0.21PZN-0.29PT and 0.49PIN-0.21PZN-0.30PT, making the ceramics of this system a promising material for high power and high temperature application. (C) 2012 Elsevier Ltd. All rights reserved.