热处理过程对纳米钛酸钡相变的影响研究

文中采用超重力反应沉淀法制备35nm的钛酸钡粉体, 并在不同温度下对粉体进行热处理, 研究了热处理过程对粉体立方→四方相变的影响。实验结果表明: 当热处理温度高于900℃时, 钛酸钡晶体结构由立方相转变为四方相, 同时粉体的粒径和四方率迅速增大, 在1 000℃时, 分别达到0.15μm和1.009;热处理过程中钛酸钡相变过程取决于粉体的粒径而与存在于晶粒中的OH^-缺陷无关; 借助于空位缺陷理论和扩散传质模型, 解释了高温热处理过程(>900℃)钛酸钡粒径迅速长大的原因。

Effect of heat treatment on phase transition of barium titanate

Barium titanate powders with size of 35nm were prepared by the high-gravity reactive precipitation (HGRP) process. The effect of heat treatment on the cubic to tetragonal phase transition of barium titanate powders was studied. XRD and TEM investigations confirmed that the phase transition occurred only when the heat treatment was above 900℃, and the particle size and the tetragonality (c/a) of the powder increased rapidly and reached 150nm and 1.009 at 1000℃, respectively. The studies also showed that the phase transition was essentially dependent on the powder size and indenpendent on the hydroxyl ions exisiting in the crystals.By means of the defects theory and the diffuse model of the crystal,the behaviour of rapod particle growth at higher heat treatment temperature(>900℃) could be explained