FANG Bijun, QIAN Kun, LING Jing, DU Qingbo
(School of Materials Science and Engineering, Changzhou University, Changzhou Jiangsu 213164, China)
Abstract: (1-x)Pb (Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) precursor powders with smaller grain size, better size distribution and less conglomeration were prepared using the partial oxalate method. Then the active precursor powders as-obtained were used to prepare PMN-PT ceramics by the conventional solid-state reaction method. XRD measurement confirmed that all the sintered PMN-PT ceramics contain slight content of pyrochlore phase. With the increase of the content of PbTiO3 (PT), the crystal structure of the PMN -PT ceramics gradually changes from rhombohedral ferroelectric phase to tetragonal. The synthesized PMN-PT ceramics exhibit high relative density. Composition and sintering conditions exert great influences on the electrical properties of the sintered PMN-PT ceramics. With the increase of the sintering temperature, the dielectric constant and the εm increase accompanied by the irregular variation of the TC/Tm, the remnant polarization Pr increases, the coercive field Ec decreases, and the piezoelectric constant d33 increases. With the increase of the PT content, the TC/Tm increases, the dielectric response changes with the ferroelectric phase transition from diffuse to normal, and the shape of the P-E hysteresis loops changes from a narrow loop to nearly a rectangle. The 0.68PMN-0.32PT ceramics sintered at 1200℃ exhibit excellent electrical properties, where εm is 14070 and Tm is 148.2℃ at 1kHz, the value of d33 reaches 457pC/N, Pr is 14.69μC/cm2, and Ec is 4.72kV/cm.
Key words: oxalate; precursor; PMN-PT; perovskite; electrical properties