共沉淀法制备Bi3.25La0.75Ti3O12纳米粉体

用硝酸铋、硝酸镧和钛酸四丁酯为原料，硝酸、无水乙醇和去离子水为溶剂，氨水为沉淀剂，采用共沉淀法合成了单相铋层状钙钛矿结构Bi3.25La0．75Ti3O12(BLT)纳米粉体。用DTA／TG和XRD研究了BLT前驱体的热行为和晶相转化过程，用场致发射扫描电子显微镜观察了BLT粉体的颗粒形貌和大小的变化。结果表明：共沉淀前驱体溶液的配制过程中，硝酸铋水解生成的硝酸氧铋不利于层状钙钛矿结构BLT相的合成。利用浓度较高的硝酸作溶剂，可以防止硝酸铋的水解，采用氨基共沉淀法直接合成出了单一相的BLT纳米粉体，在煅烧过程中，未出现Bi2Ti2O3焦绿石相。700℃煅烧2h合成的BLT粉体颗粒不大于100nm，颗粒间结合疏松，具有良好的分散性。

PREPARATION OF NANOSIZED Bi3.25 La0.75 Ti3 O12 POWDER BY COPRECIPITATION METHOD

The nanosized Bi3.25La0.75Ti3O12 (BLT) powder was prepared by coprecipitation method with chemical grade bismuth nitrateBi(NO3)35H2O], lanthanum nitrateLa(NO3)3nH2O] and tetrabutyl titanate (C4H9O)4Ti] as raw materials, nitric acid, ethanol and deionized water as solvents, and ammonia as precipitant. The Differential thermal and thermo-gravimetric analysis (DTA/TG) and X-ray diffraction (XRD) were used to investigate the thermal behavior of BLT precursor and evaluate the phase formation of BLT. Field emission scanning electron microscopy (FESEM) was employed to observe the morphology and changes of particle size of the BLT powders calcined at different temperatures. It reveals that the bismuth oxynitrate derived from bismuth nitrate hydrolysis are not favorable for the formation of BLT phase with Bi- layer perovskite structure. The bismuth nitrate hydrolysis can be avoided by using higher concentration nitric acid solution as solvent. A single phase of BLT powder can be synthesized directly by coprecipitation of the transparent BLT precursor solution into ammonia solution under stirring, and no pyrochlore Bi2 Ti2 O7 phase is found in the powder. The particle size of the BLT powder synthesized by calcination at 700 ℃ for 2 h is not larger than 100 nm and the interaction of particles is loose with good dispersion.