The effect of lead deficiency on the dielectric properties of 0.80Pb(Mg1/3Nb2/3)O3–0.20PbTiO3 ceramics

The 0.80Pb(Mg1/3Nb2/3)O3–0.20PbTiO3 ceramics with different PbO deficiency in starting raw powders were synthesized by the columbite method, and the effect of lead deficiency on phase structure, microstructure, and dielectric properties were investigated. With the increase of lead deficiency, the amount of perovskite phases of both calcined powders and sintered ceramics decreased, and at the same time, the density, linear shrinkage, and grain size also decreased greatly. When the lead deficiency varied from 0 to 1 mol%, the maximum dielectric constant jumped from 25,000 to 35,000; however, when lead deficiency was more than 1 mol%, the dielectric constant began to decrease. With the increase of lead deficiency (<1%), the increase of dielectric constant resulted from the elimination of low-permittivity PbO-rich inter-granular layers. However, this investigation proved that pyrochlore phase is less harmful to dielectric properties than PbO-rich inter-granular layers.