Si-B-O系BST玻璃陶瓷制备及介电弥散研究

Preparation and relaxer behavior of barium strontium titanate glass-ceramics doped Si-B-O sintered from sol-gel-derived powders

采用硝酸钡、硝酸锶、钛酸丁酯、正硅酸乙脂和硼酸三正丁脂为原料的溶胶凝胶方法制备了Si B O系BaxSr1-xTiO3玻璃陶瓷。通过差热分析(DTA)、热失重(TG)、X射线衍射(XRD)分析Si B O系BST玻璃陶瓷超细粉体合成过程及其相结构变化。采用X射线衍射(XRD)、扫描电子显微镜(SEM)描述Si B O系BST玻璃陶瓷烧结体的相结构和显微组织结构变化。阻抗分析仪测量Si B O系BST玻璃陶瓷的-50～100℃介电温谱。实验结果表明:Si B O系BST玻璃陶瓷粉体的相结构为立方钙钛矿相结构,其合成温度为700℃,不存在第二相。Si B O系BST玻璃陶瓷的烧结温度低于传统工艺。Si B O系BST玻璃陶瓷的显微结构呈细晶结构。Si B O系BST玻璃陶瓷的介电常数ε随着烧结温度升高而增大,介电损耗tgδ随测试温度的增加而降低。随着晶粒平均尺寸的减小,Si B O系BST玻璃陶瓷样品的介电峰变低,平坦,宽化,存在介电峰弥散化的现象。

Homogeneous Ba-Sr-Ti-Si-B-O gel has been successfully prepared by sol-gel process. Experimental results showed that perovskite barium strontium titanate phase formed at 700°C. The glass-ceramic samples were sintered at lower temperatures compared to the conventional barium strontium titanate ceramic. BST glass ceramic samples showed typical XRD patterns of perovskite polycrystalline structure and no secondary phase was detected. The dielectric permittivity of BST glass ceramic samples generally decreased as the amounts of Si-B-O glass added. The dielectric permittivity of BST glass ceramic generally increased as the sintering temperature. With the decreasing of grain size, the dielectric peaks of BST glass-ceramic samples become lower and broader. The index of relaxation (γ) of BST glass ceramic samples at the lower sintering temperature was estimated from a linear fit of the modified Curie-Weiss law. The value of γ indicated the strong relaxor nature of BST glass ceramic samples at the lower sintering temperature.