Phase transitions and dielectric properties of (1−x)Pb(In1/2Nb1/2)O3(PIN)‐xPbZrO3(PZ) solid solution system have been examined as a function of the concentrationx. Two morphotropic phase boundaries were identified: (1) pseudocubic to rhombohedral phase boundary atx=0.35 and (2) rhombohedral to orthorhombic atx=0.8. Forx<0.35, a diffuse phase transition was observed. For 0.35<x<0.8, the relative permittivity &egr;’rshowed a sharp peak atTc. In this regime, the phase belowTcwas confirmed to be ferroelectric by observation squareP‐Ehysteresis loops. Forx≳0.8, a steplike dielectric anomaly appeared atTt(belowTc) as well as the sharp peak in the permittivity. The phase belowTtwas confirmed to be antiferroelectric by the observation of doubleP‐Ehysteresis loops. The maximum permittivity of 15 000 (at 100 kHz) was observed atx=0.35 ©1995 American Institute of Physics.