| 摘要 |
<p>Disclosed is a method for producing a high-purity tungsten powder that has a phosphorus content of less than 1 ppm by weight, which is characterized in that: an ammonium tungstate solution that contains phosphorus, which is an impurity, in an amount of not less than 1 ppm by weight in terms of the inclusion in tungsten is used as a starting material; the ammonium tungstate solution is neutralized with hydrochloric acid at a temperature of 50°C or less to have a pH of 4 or more but less than 7, so that ammonium paratungstate undecahydrate crystals are precipitated; the resulting solution is heated to 70-90°C and filtered at a high temperature, so that ammonium paratungstate pentahydrate crystals are obtained; the ammonium paratungstate pentahydrate crystals are calcined so as to form tungsten oxide; and then the tungsten oxide is subjected to hydrogen reduction so as to obtain a high-purity tungsten powder. Also disclosed is a method for producing a high-purity tungsten powder that has a phosphorus content of not more than 0.4 ppm by weight, which is characterized in that the pH during the step of neutralization with hydrochloric acid is set at 4-6 (inclusive) and a high-purity tungsten powder is produced by the same procedure as described above. Consequently, the phosphorus content can be efficiently reduced.</p> |
