Phase transformation, oxidation and hydration of praseodymium sesquioxide

Abstract

The C→A transformation of Pr₂O₃ has been examined. The transformation is sluggish and takes place at and above 750°C. C-Pr₂O₃ is oxidized at a lower temperature than the A-form and oxidation proceeds in two stages in both cases. A hydrate Pr₂O₃ H₂O, formed by the interaction of C-Pr₂O₃ and water at relatively high temperature, is described and its behaviour compared with that of Pr(OH)₃. The C-form undergoes hydration at 40°C while the A-form does not. All the observations have been explained in terms of the defect structure of C-Pr₂O₃.