Sr_(1-x)La_xTiO_3陶瓷的介电特性与缺陷机构

DIELECTRIC PROPERTIES AND DEFECT STRUCTURE OF Sr_(1-x)La_xTiO_3 CERAMICS

研究了组份为Sr_(1-x)La_xTiO_3(其中x=0—0.06)陶瓷的介电特性与缺陷机构。发现:当x=0.0005—0.01时,在频率为10~5—10~7Hz范围内,材料出现了介电弛豫现象;而当0.02≤x≤0.05时,在频率为10~3—10~7Hz范围内,材料没有发生介电弛豫。材料的电阻率与La含量的关系呈“U”型曲线变化。作者采用La替代Sr后而产生的电子补偿与锶空位缺陷补偿分別存在或共同存在,以及空间电荷极化机制对上述现象作出了解释。另外由正电子湮没寿命谱得到的有关材料缺陷机构的结论则进一步证明了该解释的合理性。

The dielectric properties of Sr_(1-x)La_xTiO_3 ceramics (0≤x≤0.06) were measured in a frequency range from 10~5 to 10~7 Hz at 25℃. The results show that the dielectric properties and the charge compensation mechanism vary obviously with La content. When x<0.02, the charge compensation is achieved by quasifree electrons and strontium vacancies in the materials. The inhomogeneous distribution of quasi-free electrons causes the space-charge polarization and the dielectric relaxation in the range of 10~5—10~7 Hz. When 0.02≤x≤0.06, the ionized lanthanum is compensated by strontium vacancies and the relaxation phenomenon disappears in the tested frequency range.Positron annihilation technique (PAT) was adopted to study the defect structure further. The lifetime spectrum measured clearly indicates that the defect model for different La contents is reasonable