Reaction Kinetics of Perovskite Phase Formation in Lead Zinc Magnesium Niobate Ceramics

The reaction kinetics of perovskite Pb[(Zn,Mg)_1/3Nb_2/3]O₃─SrTiO₃ (PZMN–ST) phase formation vary with the phase condition of the starting materials. Basically, the reaction is controlled by a diffusion process with either a fixed number of nuclei or a constant nucleation rate. When the Pb₃Nb₂O₈ (P₃N₂) phase is used as the starting material, the reaction belongs to the former. The P₃N₂ phase acts as a nucleation center and fixes the number of nuclei for perovskite phase formation. If PbO and Nb₂O₅ instead of P₃N₂ are used as starting materials, the nucleation center will be the pyrochlore phase Pb₂Nb₂O₇ or P₃N₂ and is continuously created by the reaction of residual PbO with the formed pyrochlore Pb₃Nb₄O₁₃ phase. In the final stage of PZMN formation, the reaction is mainly through diffusion of ZnO into PMN or Zn‐containing PMN. The importance of the pyrochlore phase to perovskite PZMN phase formation is consequently asserted.