EFFECT OF THE CRYSTAL STRUCTURE ON THE ACID DISSOLUTION OF ZIRCONIUM OXIDE.

Abstract

The acid dissolution of zirconia is important for the reprocessing of nuclear fuel elements containing zirconia as a diluent and for the hydrometallurgy of baddeleyite ore (ZrO//2). CaO-stabilized zirconia was prepared by a solid-state diffusion process and dissolved in a nitric acid/hydrofluoric acid mixture. The dissolution curves of cubic-monoclinic mixed phase zirconia consist of two parts, indicating rapid and slow dissolution, respectively. The relation between the amount of rapidly dissolving phase and the amount of CaO added coincides with the relation between the fraction of the cubic phase present and the amount of CaO, so that it was concluded that the cubic phase of zirconia is very soluble. Tetragonal phase prepared by the addition of CeO//2 was also soluble.