化学共沉淀法制备正铌酸镧过程中杂相的形成与控制

Formation and control of byproduct produced during process of making LaNbO_4 by coprecipitation approach

从多酸化学的角度 ,讨论了在化学共沉淀法制备正铌酸镧 (LaNbO4 )过程中 ,不同 pH条件对产物相组成的影响。结果表明 :在酸性条件下 ,由于同多酸盐的析出 ,产物中有部分偏铌酸镧相K2 LaNb5O15存在 ;在碱性条件下 ,由于铌酸盐的水解受到抑制 ,可以制备得到相组成相对单一的正铌酸镧相 ;对酸性条件下得到的无定形前驱体粉末进行碱化处理可以降低烧成正铌酸镧相中的杂相含量。

Lanthanum orthoniobate (LaNbO 4) amorphous precursors are prepared by coprecipitation approach, using K 3NbO 4 and LaCl 3 as the raw reagents. From polyacid chemistry, the influence of homo-polyniobate on the phase constitution of LaNbO 4 is investigated. The XRD patterns reveal that the hydrolization of niobate can be restrained in an alkaline system, so pure LaNbO 4 can be obtained. The DSC analysis also confirms that in an acid system, there is byproduct K 2LaNb 5O 15 in the product due to the hydrolization of homo-polyniobate. The content of K 2LaNb 5O 15 in acid powder can be reduced by alkaline treatment.