Effects of PbO content on the microstructure and dielectric constant of 0.8Pb(Zn1/3Nb2/3)O-3-0.1BaTiO(3)-0.1PbTiO(3)

The microstructure and the dielectric constant of 0.8Pb(Zn1/3Nb2/3)O-3-0.1BaTiO(3)-0.1PbTiO(3) (mol fraction) change considerably with the PbO content. A single perovskite phase was observed to form in specimens with 0.25 or 0.5 wt% PbO deficiency. When the PbO content increased above these values, a liquid phase formed and was present between perovskite grains. As the level of PbO decreased in the specimens, on the other hand, a pyrochlore phase and a ZnO phase formed, as second phases. The pyrochlore grains were sometimes much larger than the perovskite grains. The densification was considerably suppressed with decreasing PbO content. The dielectric constant showed a maximum of 22,000 in the specimen with 0.5 wt% PbO deficiency The presence of a second phase and the reduction in the sintered density reduced the dielectric constant considerably. The liquid phase, however, was found to be more harmful than the pyrochlore and ZnO phases to the dielectric constant of the material.