Normal-Relaxor-Diffuse Ferroelectric Phase Transition and Electrical Properties of Bi(Mg1/2Ti1/2)3-PbZrO3-PbTiO3 Solid Solution Ceramics Near the Morphotropic Phase Boundary

Perovskite-type xBi(Mg1/2Ti1/2)O3-(0.56-x)PbZrO3-0.44PbTiO3 (xBMT-PZ-PT) ternary solid solution ceramics were synthesized via a conventional solid-state reaction method. The phase transition behaviors, dielectric, ferroelectric, and piezoelectric properties were investigated as a function of the BMT content. The X-ray diffraction analysis showed that the tetragonality of xBMT-PZ-PT was enhanced with increasing the BMT content, and a morphotropic phase boundary (MPB) between rhombohedral and tetragonal phases was identified approximately in the composition of x=0.08. In addition, the dielectric diffuseness and frequency dispersion behavior were induced with the addition of BMT and a normal-relaxor-diffuse ferroelectric transformation was observed from the PZ-rich side to the BMT-rich side. The electrical properties of xBMT-PZ-PT ceramics exhibit obviously compositional dependence. The x=0.08 composition not only possessed the optimum properties with epsilon T33/epsilon 0=1450, Qm=69, d33=390pC/N, kp=0.46, Pr=30C/cm2, Ec=1.4kV/mm, Tc=325 degrees C, and a strain of 0.174% (d33*=436pm/V) under an electric field of 4kV/mm as a result of the coexistence of two ferroelectric phases near the MPB, but also owned a good thermal-depolarization behavior with a d33 value of >315pC/N up to 290 degrees C and a frequency-insensitive strain behavior.