Dielectric properties of PMN-PT ceramics near the morphotropic phase boundary

Relaxor ferroelectric (1-x) Pb(Mg_1/3 Nb_2/3)O_3-x PbTiO₃ (PMN-PT) ceramics near the morphotropic phase boundary were prepared by the columbite precursor method. The phase composition and phase structure of ceramic samples was investigated by X-ray diffraction analysis, the results show that pure perovskite phase was obtained for all the specimens and no other phase was detected. Moreover, there exists a morphotropic phase boundary (MPB) for the composition at x = 0.33, and the rhombohedra phase and tetragonal phase coexists for the composition near MPB, but the pure rhombohedra phase and tetragonal phase separately exists for the composition away from MPB. While the PT content increased for the composition near MPB, the dielectric peak become sharp and the frequency diffusion weakened, namely the dielectric relax degree weakened. This is mainly ascribed to the tetragonal phase increase and the rhombohedra phase decrease. Thereby, the relaxor ferroelectric is transformed to normal ferroelectric.