晶粒尺寸对Ba_(0.70)Sr_(0.30)TiO_3陶瓷介电性能的影响规律及机理研究

Grain size dependence of the dielectric propertiesof Ba_(0.70)Sr_(0.30)TiO_3 ceramics and its mechanisms

通过制备晶粒尺寸处于0.1—10μm之间的致密Ba_(0.70)Sr_(0.30)TiO_3陶瓷,系统研究了晶粒尺寸对居里温度TC、铁电相介电常数εF、峰值介电常数εM的影响规律,并深入分析了其内在的影响机理.研究表明:晶粒尺寸减小时,TC刚开始基本不变,直到晶粒尺寸小到一定程度时才开始降低,此变化规律可由Buesseum的内应力模型解释;随晶粒尺寸的增加,εF先增加后减小,此变化规律可由Shaikh的串并联模型来解释,主要影响因素有内应力、畴、晶界;εM随晶粒尺寸的增加,在晶粒尺寸较小时先增加后减小,晶粒尺寸较大时略有增加,此变化规律可由弥散相变理论和串并联模型共同解释,在晶粒尺寸较小时主要影响因素为内应力、微畴和晶界,晶粒尺寸较大时主要影响因素为晶界.

By successfully fabricating dense Ba0.70 Sr0.30TiO3 ceramics in the size range of 0.1--10μm, the grain size dependence of the Curie temperature Tc, dielectric constant in ferroelectric phase er and in peak eM were systematically investigated. The results show that Tc will not decrease considerably until the grain size becomes small enough. This can be explained by Buesseum＇s internal stress model. As the grain size increases, eF increases first and decreases afterward, which can be interpreted by Shaikh＇s series-parallel model, The main active factors are internal stress, domain and grain boundary. On the other hand,if the grain size is small, e u increases first and decreases afterward as the grain size increases. If the grain size is bigger, e M increases slightly, This can be explained by the diffuse phase transition theory and series-paralled model. The main active factors are grain boundary, internal stress, for small grain sizes, and domain and grain boundary for bigger grain sizes, respectively.