三种化学方法合成K0.5Bi0.5TiO3粉体的机理比较

采用溶胶-凝胶法、水热法和溶胶-凝胶-水热法三种化学方法合成K_0.5Bi_0.5TiO₃ (KBT)无铅压电陶瓷粉体. 用X射线衍射(XRD)分析产物的结构, 用扫描电镜(SEM)和透射电镜(TEM)观察产物的形貌. 实验结果表明, 三种化学方法均可获得纯钙钛矿相KBT粉体, 但不同工艺获得的粉体在形貌和生成机制上有很大的不同. 溶胶-凝胶法属高温固相扩散机制, 需要700 ℃以上温度煅烧才可获得KBT纯相, 且粉体颗粒度大、团聚严重. 水热法符合溶解-结晶机制, 生长出四方形的KBT纳米片. 溶胶-凝胶-水热法利用了凝胶团聚体空间链状结构的模板作用, 通过原位结晶机制生长出KBT纳米线.

Comparative Study of Formation Mechanism of K0.5Bi0.5TiO3 Powders Synthesized by Three Chemical Methods

Lead-free piezoelectric powders, K_0.5Bi_0.5TiO₃ (KBT), were synthesized by sol-gel, hydrothermal and sol-gel-hydrothermal methods, respectively. The structures and morphologies of the powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the pure perovskite KBT powders can be obtained by all three methods; however, the formation mechanism and morphology evolution of powders prepared by various processes are quite different. It was deduced that the solid diffusion mechanism was applied to sol-gel process. Due to the high-temperature treatment above 700 ℃, the KBT powders produced by sol-gel method had large size with serious agglomeration. The cubically shaped nanopowders were prepared by hydrothermal method, which belongs to dissolution-crystallization mechanism. The in-situ transformation mechanism was applied to sol-gel-hydrothermal process, and gel clusters played a crucial role in the formation of nanowire morphology.