Preparation of uniform colloidal particles of hafnium compounds

Abstract

Spherical colloidal particles of amorphous hafnium hydroxysulphate of narrow size distribution have been prepared by ageing at room temperature acidic solutions of hafnium oxychloride in the presence of metal sulphates. On calcination the powders crystallized into monoclinic hafnia, yet retained their spherical shape. The effects of several parameters (concentration of reagents, nature of the acid and the sulphate salt) on the characteristics of the precipitated particles were studied in detail. A mechanism for the formation of such particles is suggested.