Effecting Preparation of pyrochlore-type Tungsten oxides Factors

(1) Preparation of solution acidity pyrochlore-type oxides need not be confined to the desired acidic range, previous researchers summarized pH range (3.5 to 6.0) are not powder preparation must environment, the pH range that extends 3.5 ~ 8.9.

(2)Sodium tungstate solution pH or not cause a significant impact on the average particle size of the product; different additives can create a huge difference in the pH of the environment in the hydrothermal system, select the appropriate additives is to prepare pyrochlore The key factor of the tungsten oxide type.

(3) The size of the pH value of the reaction rate on the one hand will cause a major impact, pH smaller the faster the reaction rate; the other hand, the final solution will affect the decomposition rate, i.e. less than 7, the solution to generate complex tungsten-containing complex ions resulting solution structure changed dramatically, partly stable complex ions in solution are not easily transformed, resulting in W element can not be all entered H2W2O7 precipitate. From the simultaneous pursuit of the reaction rate, the decomposition rate of the final solution, the angle of view, the optimal conditions for the preparation of tungsten oxide pyrochlore type for pH≈7.

(4) Preparation of pyrochlore-type process, H + and reaction equivalent ratio WO42- 2 is more likely, according to the findings consistent element conservation law and the law of conservation of charge determined by the overall reaction scheme.

(5) Dosage and reactant solution temperature both will affect the reaction rate, the influence of can be summarized as follows: a solution at the same pH conditions, the reactants the higher the dose, the faster the reaction rate: the guaranteed reactants does not occur Under the premise of change, the higher the temperature, the faster the reaction rate.

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