Abstract: The phases of tungsten blue oxides produced by the light reduction of ammonium paratungstatc (APT) with hydrogen vary with the reduction temperature. The product reduced at 275℃ is noncrystalline ammonium tungsten bronze (ATB) and at 325℃ is crystalline ATB. The content of ATB in the reduced product gradually decreases with increasing the reduction temperature. There is no ATB in the product reduced at 575℃. The phase W₂₀O₅₈ appears above 325℃. Its content increases with the reduction temperature and reaches its maximum at 525℃, and then it decreases sharply above 525℃. The phases WO₂ and β-W appear at 525℃. The phase α-W appears between 525℃and 575℃.The phases of the products reduced at 525-575℃change remarkably from ATB andW₂₀O₅₈ to WO₂, β-W and α-W. The quantitative relationship between the phases of tungsten blue oxide and the reduction temperature of APT has been studied in this paper.
When WO₃ is lightly reduced by hydrogen, W₂₀O₅₈ appears at certain temperature between 425℃ and 525℃; W₁₈O₄₉ appears between 475℃ and 525℃; A little β-W appears at 625℃. When the reduction temperature is higher than 625℃, the content of α-W in the reduction product rapidly increases with the reduction temperature.
When APT is lightly reduced by hydrogen, β-W can be obtained at a very wide temperature range, compared with WO₃also reduced by hydrogen. The content of β-W obtained from APT is more than that obtained from WO₃.
When APT is reduced by hydrogen at 450℃ for five minutes, the product is crystalline ATB.If the reduction time is longer than five minutes, W₂₀O₅₈ phase will appear. The content of W₂₀O₅₈ increases gradually with the reduction time and at the same time the content of ATB decreases gradually. When the reduction of APT with hydrogen is carried out at 450℃, the relationship between the phases of tungsten blue oxide and the reduction time has been experimentally investigated in this article.