溶胶-凝胶方法制备KTa_(0.65)Nb_(0.35)O_3薄膜的凝胶化和热处理研究

Study of the Gelation and Heat-Treatment of KTa_(0.65)Nb_(0.35)O_3 Thin Films Prepared by Sol-Gel Process

本文较系统地研究了溶胶-凝胶方法制备 KTa_(0.65)Nb_(0.35)O_3薄膜的凝胶化行为和热处理.用自制的金属醇盐KOC_2H_5、Nb(OC_2H_5)_5和 Ta(OC_2H_5)_5为原料,无水乙醇作溶剂,配制均匀的溶液.实验结果表明,溶液浓度、介质或催化剂的使用、匀胶时的环境温度和湿度及单层膜厚等因素对凝胶薄膜的形成有较大影响.条件适宜时可得到与衬底附着紧固的均匀透明的凝胶薄膜.随着热处理温度升高,薄膜首先从非晶态结晶成焦绿石结构的 KTN 相,然后在更高的温度转变成钙钛矿相.不同的衬底所需的烧结温度不同,烧成后薄膜的晶粒取向也不同.为彻底排除薄膜内的酸根、有机基团和碳元素,热处理温度不宜低于700℃.

The gelation and the heat-treatment of the KTa_(0.65)Nb_(0.35)O_3 thin films prepared by spin-ning method in sol-gel process are investigated in this paper systematically.Homogeneous andstable KTN coating solutions were prepared from KOC_2H_5,Ta(OC_2H_5)_5,and Nb(OC_2H_5)_5in absolute ethanol with a key additive of benzene or acetic acid.Experimental results showthat the formation of the gel films will strongly depend on some spinning conditions,such asthe solution concentration,the environment temperature and moisture,the application of ad-ditive,and the single layer thickness of the films.Under the suitable conditions,the uniformtransparent gel films adhered firmly on substrates can be obtained.The thickness of the filmshas to be built up gradually by successive spinning process in order to reduce the stress de-veloped during the heat-treatment.Along with the temperature rising of heat-treatment,thetransitions from amorphous state to pyrochlore phase at 600℃ and then to perovskite phase athigher temperature occur.Phase structure and grain orientation of the films strongly dependon calcining temperature and substrate conditions.In order to remove completely the aceticligands,organic groups,and residual carbon element in the films,the annealing temperaturemust be higher than 700℃.