晶粒尺寸对细晶钛酸钡陶瓷介电、压电和铁电性能的影响

Grain Size Effect on Dielectric, Piezoelectric and Ferroelectric Property of BaTiO_3 Ceramics with Fine Grains

以采用水热法制备的BaTiO_3粉体作为原料,利用普通烧结法和两步烧结法制备出晶粒尺寸为0.25~10.15μm的BaTiO_3陶瓷,研究了晶粒尺寸效应对BaTiO_3陶瓷的介电、压电以及铁电性能的影响。结果表明:BaTiO_3陶瓷的四方相含量随着陶瓷晶粒尺寸的增大而增加;当晶粒尺寸在1μm以上时,室温相对介电常数(e￠)和压电系数(d33)随着晶粒尺寸的减小而增大,并在晶粒尺寸为1.12μm时分别达到最大值5628和279 p C/N,然后两者随着晶粒尺寸的进一步减小而迅速下降。BaTiO_3陶瓷的剩余极化强度Pr随晶粒尺寸的增大而提高,而矫顽场Ec却呈现出相反的趋势。晶粒尺寸对介电性能和压电性能的影响是由于90°电畴尺寸和晶界数量的变化。晶粒的晶体场和晶粒表面钉扎作用的变化影响了电畴,进而改变电滞回线。

A series of highly dense barium titanate（Ba Ti O3） ceramics with average grain size ranging from 0.25 ？m to 10.15 μm were prepared by either conventional sintering or a two-step sintering method, using ultrafine Ba Ti O3 powders prepared by hydrothermal approach. The impact of grain size on dielectric, piezoelectric and ferroelectric properties of Ba Ti O3 ceramics was investigated. Results indicate that the tetragonal phase of Ba Ti O3 ceramics increases with the increase of grain size. When the averaged grain size is above 1 μm, the relative dielectric constant（？？） and piezoelectric coefficient（d33） at room temperature increase firstly with the decrease of grain size, with the maximum values of 5628 and 279 p C/N, respectively, at the grain size of 1.12 μm, and then decrease rapidly with further decrease of the grain size. The remanent polarization Pr of Ba Ti O3 ceramics rises with the increase of grain size, but the coercive field Ec exhibits opposite tendency. The variation of dielectric and piezoelectric properties resulted from the change of grain size is regarded as the impact of 90？ domain size and the number of the grain boundaries, while the change of hysteresis loops is due to the change of the crystal field in the grains and the ＂pinning＂ effect of the surface layer on the grains.