Effects of PbO excess in Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ ceramics: Part I. Sintering and dielectric properties

The influence of the presence of free PbO on densification, the perovskite/pyrochlore phase ratio, and corresponding dielectric properties has been studied for 0.9 PMN–0.1 PT-based ceramics with different added PbO excess. The sintering behavior of PMN-PT-based ceramics was basically controlled by PbO losses. However, the presence of a rich-PbO liquid phase during sintering produced pyrochlore grains, mainly located at the surface of the specimens. The dielectric properties of the PMN-PT-based materials, fabricated with different values of PbO excess, were similar when the secondary phase preferentially located at the surface was removed by polishing prior to electrode deposition. The thickness of the PbO-rich intergranular layers of the four samples with different initial PbO content was mainly independent of the amount of PbO excess because most of the free PbO was eliminated during sintering. Dielectric constant values of approximately 17,000 at 1 kHz and 40 °C were measured.