采用软化学法制备WO3和其锂化物及其结构稳定性的研究

通过两种方法合成了六方形和单斜氧化钨的水化物WO3·yH2O(y=0.50～1.20):(1) 用强酸(1～3 mol/L HCl) 将0.25 mol/L Li2WO4在100 ℃进行酸化; (2) 将1 mol/L Li2WO4置于高压反应釜中,控制pH为1.5,在100 ℃进行水热合成. 对于水热法,温度较高时(125～200℃),得到组分为LixWO3+x/2·yH2O(x=0.10～0.50,y=0.50～0.90)的锂化氧化钨. 合成产物的结构和组分与酸的浓度和后处理(加热、超声波)有关. 在350 ℃加热时六方形氧化钨完全转化为单斜氧化钨. 将温度在150 ℃以上时通过水热法合成的氧化钨前驱体进行超声波处理,产物的含锂量恒定为每单元0.18摩尔. 锂的引入有利于锂化氧化钨的结构和组分的稳定.

Synthesis of Tungsten Trioxide and Lithiated Tungsten Oxides by a Soft Chemistry Route and Their Structural Stability

Hexagonal and monoclinic tungsten hydrates, WO3·yH2O (y=0.50 -1.20) were obtained by acidification of Li2WO4(0.25 mol/L) with a strong acid (1-3 mol/L HCl) at 100 ℃,and by a hydrothermal procedure carried out in an autoclave at 100 ℃ using Li2WO4 (1 mol/L) and a controlled pH of 1.5. Applying the hydrothermal procedure at a higher temperature of 125-200 ℃, however, resulted in the formation of hexagonal lithiated tungsten oxides of composition LixWO3+x/2·yH2O (x=0.10 - 0.50,y=0.50 - 0.90). The structure and composition of the products are dependent on the acid concentration and post treatments such as heating and ultrasonication. The conversion of hexagonal tungsten trioxide to the monoclinic form could be accomplished by heating at 350 ℃. Ultrasonic treatment of the oxide precursors from hydrothermal procedure above 150 ℃ results in a product with a constant lithium content amounting to 0.18 per unit cell which is accountable for the structural and compositional stability of lithium tungstate.