Stabilization of perovskite phase and dielectric properties of Pb(Zn, Mg)_1/3Nb_2/3O₃-PbTiO₃ ceramics prepared by excess constituent oxides

The perovskite phase in PZN-PMN-PT (PbZn_1/3Nb_2/3O₃-PbMg_1/3Nb_2/3O₃-PbTiO₃) pseudoternary ceramics was stabilized by the addition of excess constituent divalent oxides (PbO, MgO, and ZnO). 5 mol% excess MgO or 7.5 mol% excess PbO was sufficient to eliminate the remnant cubic pyrochlore phase after sintering at 1100 °C for 1 h. The enhanced diffuse phase transition (DPT) and the decrease in the electrical resistivity were observed in the presence of excess ZnO or MgO. These were interpreted in terms of the additional formation of negatively charged, short-range ordered 1: 1 domains with a concomitant generation of charge carriers (holes). The behavior of excess MgO or ZnO at concentrations above 5 mol% was studied by examining complex impedance patterns.