Preparation of Electro-conductive White Fine Powders Coated with SnO2-Sb Film

A novel method was developed for preparation of white fine powders coated with ATO. A fine powder of rutile type TiO2 was homogeneously coated with a mixed hydroxide film of ATO composition by simultaneous adding an acidified metal chlorides solution and an alkaline solution to maintain the suspension pH at definite levels in either a single stage or double stages at 343K. The pH range applicable to hydrolysis of metal chloride solutions of ATO composition onto substrate powder is far wider than with ITO coating. Heating of the resulting powders at 923K or above is necessary to attain electro-conductivity. Increasing the weight ratio of the Sb/SnO2 sharply decreases the specific resistance, which then reaches an almost constant value at Sb/SnO2 weight ratios above 016. Increasing the Sb/SnO2 weight ratio also causes color changes in the product, with L and b values decreasing almost linearly with the Sb/SnO2 weight ratio. A low hydrolysis pH results in better electro-conductivity of the final product.