Pb (In1/2Nb1/2) O-3-Pb (Sc1/2Nb1/2) O-3-PbTiO3 (PIN-PSN-PT) ternary ceramics with compositions near morphotropic phase boundary (MPB) were fabricated by solid-state-sintering process. Dielectric and piezoelectric properties of xPIN-yPSN-zPT (x = 0.19, 0.23 and z = 0.365, 0.385) ceramics were investigated as a function of temperature, showing high Tr-t and T-c on the order of 160 similar to 200 degrees C and 280 similar to 290 degrees C, respectively. The xPIN-yPSN-0.365PT (x = 0.19 and 0.23) ceramics do not depolarize at the temperature up to 200 degrees C, showing a better thermal stability when compared to the state-of-the-art relaxor-PbTiO3 systems. A slight variation (<9%) of k(p), k(t), and k(33) was observed in the temperature range of 25 degrees C-160 degrees C for xPIN-yPSN-0.385PT (x = 0.19 and 0.23) ceramics. Rayleigh analysis was employed to quantify the contribution of domain wall motion to piezoelectric response, where the domain wall contribution was found to increase with composition approaching MPB for PIN-PSN-PT system.