Mechanism of Formation of Perovskite Phase and Dielectric Properties of Pb(Zn,Mg)1/3Nb2/3O3 Ceramics Prepared by Columbite Precursor Routes

Abstract

The mechanism of formation of the perovskite phase and the dielectric properties of Pb(Zn,Mg)1/3Nb2/3O3 (PZMN) ceramics were examined using two different types of columbite precursors, (Mg,Zn)Nb2O6 (MZN) and MgNb2O6+ ZnNb2O6 (MN + ZN). The formation of perovskite phase in the PbO + MN + ZN system is characterized by an initial rapid formation of Mg-rich perovskite phase, followed by a sluggish formation of Zn-rich perovskite phase. On the other hand, due to the formation of pyrochlore phase of mixed divalent cations Pb2–x(Zn,Mg)yNb2−yO7−x−3y/2, the pyrochlore/perovskite transformation in the PbO + MZN system proceeded uniformly with a spatial homogeneity. Further analysis suggested that the formation of perovskite phase is a diffusion-controlled process. The degree of diffuseness of the rhombohedral/cubic phase transition (DPT) is higher in the PbO + MN + ZN system than in the PbO + MZN specimen for T > Tmax (temperature of the dielectric permittivity maximum), indicating a broadened compositional distribution of the B-site cations in the PbO + MN + ZN system.