准同型相界附近PMN-PT陶瓷的介电性能

采用铌铁矿预产物合成法制备了组成在相界附近的(1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3(PMN-PT)弛豫铁电陶瓷。陶瓷样品X-射线衍射相组成和相结构分析表明:所有陶瓷样品均为纯钙钛矿相,无任何其他杂相出现;且组成在x=0.33处存在一准同型相界(MPB),在该相界附近三方相和四方相共存,而远离该相界则分别为纯三方相和四方相。相界附近组成随PT摩尔分数增加,介电峰变得尖锐,频率弥散减弱,即介电弛豫程度减弱。这主要是由于四方相增多,三方相减少,从而使弛豫铁电体变为正常铁电体。

Dielectric Properties of PMN-PT Ceramics Near the Morphotropic Phase Boundary

Relaxor ferroelectric(1-x) Pb(Mg1/3Nb2/3)O3-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.