The full set of material constants for relaxor-based ternary single crystals Pb (In1/2 Nb1/2) O3 -Pb (Mg1/3 Nb2/3) O3 - PbTiO3 (PIN-PMN-PT) were determined and compared to binary Pb (Mg1/3 Nb2/3) O3 - PbTiO3 (PMNT) crystals. The Curie temperature for rhombohedral compositions of PIN-PMN-PT was found to be in the range of 160-200 °C with ferroelectric rhombohedral to tetragonal phase transition on the order of 120-130°C, more than 30°C higher than that found for PMNT. The piezoelectric coefficients (d33) were in the range of 1100-1500 pC/N, with electromechanical coupling factors (k33) about 89%-92% comparable to PMNT crystals. The coercive field of the ternary crystal was found to be 5.5 kV/cm, double the value of the binary counterparts. The dielectric behavior under varying dc bias exhibited a similar trend as observed in PMNT with a much broader usage temperature range. Together with its enhanced field induced phase transition level, the ternary PIN-PMN-PT crystals are promising candidates for high temperature and high drive transducer applications. © 2008 American Institute of Physics.