Dielectric and Ferroelectric Properties of Bi(Zn_1/2Ti_1/2)O₃-PbTiO₃—PbZrO₃Ternary Ceramics

Ceramics of a new ternary solid solution system, xBi(Zn₁/₂Ti_1/2)O₃-2/PbTiO₃-zPbZrO₃ (xBZT-y/PT-zPZ), with compositions along the solubility limit curve are prepared by solid-state reaction and sintering technique. Two morphotropic phase boundaries (MPBs) separating the orthorhombic and tetragonal (mpbo-t) phases and the tetragonal and rhombohedral (mpbt-r) phases, respectively, are observed with increasing z (0.10 < x < 0.21; 0 < y < 0.49). It is found that the transition from the ferroelectric to paraelectric phase becomes more diffuse with the addition of BZT into the PZT solid solution. Enhanced dielectric and ferroelectric properties appear at MPB_R-T, which exists over a wide composition region (0.45 < z < 0.6), as revealed by X-ray diffraction and dielectric measurements. The dielectric constant reaches a maximum value (ε' = 1250) on the tetragonal majority side of the MPB. The highest remnant polarization (P_r = 34.2 µC/cm²) is found in the composition at the center of the MPB, where the rhombohedral and tetragonal phases coexist in almost equal quantities.