Binary Oxides of Uranium

The most common oxides are uranium dioxide (UO2), uranium trioxide (UO3), triuranium octoxide (UjOg), and uranyl peroxide (UO4 or UO2 Oj). The main properties of these compounds are summarized in Table 1.5. It should be noted that there are several other oxides in which the oxidation states are not well defined as either tetra-valent or hexavalent, like UO2.1, U2O5, U3O7, U12O35, etc. Detailed discussions of the uranium-oxygen system and its complex phase diagram were presented elsewhere, for example, by Allen and Tempest (1982) and Grenthe (2006). 

Uranium trioxide (UO ) is a hexavalent binary compound that appears mainly as an orange-yellow powder with a density of 5.5-8.7 g cm and melting point of 200°C-650°C. The broad range of densities and melting points is derived from the strong dependence of the compound on the crystalline form (a, p, y, and 8) and 

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