The effect of pyrochlore phase on formation mechanism and electrical properties of perovskite PZMN relaxors

The reaction mechanism and electrical properties of phase formation of the perovskite Pb[(Mg_x,Zn_1-x)_1/3Nb_2/3] O₃-SrTiO₃ (PZMN-ST) were studied. Three major pyrochlore phase types, Pb₂Nb₂O₇, Pb₃Nb₂O₈ and Pb₃Nb₄O₁₃ were characterized and analyzed to understand their roles in the formation of perovskite PMN, PZN and PZMN phases. The formation of a perovskite phase within PMN relaxors requires the presence of either Pb₂Nb₂O₇ or Pb₃Nb₂O₈ pyrochlore phases in the mixture and is only slightly dependent on the presence of the stabilizer. On the other hand, the formation of a perovskite phase within PZN or PZMN relaxors requires the presence of both Pb₃Nb₂O₈ pyrochlore phase and stabilizer. The maximum dielectric constant for PMN, PZN and PZMN systems can be obtained with the Pb₃Nb₂O₈ phase present in the starting raw materials because of the benefit of Pb₃Nb₂O₈ to perovskite phase formation.