Preparation of Al2–xYxW3O12 powders by citrate sol-gel process

Al2−xYxW3O12 (x=0.2, 0.5, 0.8, 1.0, 1.2, 1.5, 1.7 and 2.0) powders were synthesized by citrate sol-gel process. The concentration of species in a citric solution for preparing Al2−xYxW3O12 powders was calculated. The powders were characterized by differential thermal analysis(DTA), thermogravimetry(TG), X-ray diffractometry(XRD) and scanning electron microscopy(SEM), respectively. No solid solution of Al2−xYxW3O12 is formed with x values varying from 0 to 2.0. The maximum solid solubility of Y2O3 in Al2W3O12 and Al2O3 in Y2W3O12 is less than 0.5. Y2W3O12 easily absorbs water in air and forms a composition of Y2W3O12·3.2H2O, and Al2W3O12 forms Al2W3O12·0.17H2O in the same condition.