BaTiO3超微粉及其在陶瓷中的晶粒尺寸效应

用Ｓｏｌ－Ｇｅｌ法制备了ＢａＴｉＯ３超微粉并经烧结获得了不同粒径的陶瓷。用Ｘ射线衍射研究了室温晶体结构。在粉末压块和陶瓷上测得了介电常数的温度依赖性。介电常数－温度曲线表明，随着晶粒尺寸减小，居里温度降低，而四方－正交以及正交－三角相变温度升高。在晶粒尺寸减小过程中，三个介电峰逐步降低和宽化并按如下顺序最终消失：三角－正交，正交－四方和四方－立方。用介电测量确定了铁电性消失的临界尺寸，其值与文献中

Grain Size Effect in BaTiO_3 Ultrafine Powders and Ceramics

BaTiO3 ultrafine powders are prepared by Sol-Gel method and ceramics with various grain sizeare obtained by firing the powders at different temperatures. The room temperature crystal structure isstudied by X-ray diffraction. The temperature dependence of the dielectric constant is obtained usingpressed powders as well as ceramics. Dielectric peaks show that when the grain size decreases, the Curietemperature decreases while the tetragonal-orthorhombic and orthorhombic-rhombohedral transitiontemperatures increase. With decreasing grain size, the three dielectric peaks lower and broaden andeventually disappear in the following sequence: rhombohedral-orathorhombic,orthorhombic-tetragonaland tetragonal-cubic. The critical size at which ferroelectricity disappears is determined by dielectricmeasurement. Its value is in agreement with that obtained by crystal ratio meassurement in the literature.