Further insights into the chemistry of the Bi–U–O system
Cubic fluorite-type phases have been reported in the UIVO2–Bi2O3 system for the entire compositional range, but an unusual non-linear variation of the lattice parameter with uranium substitution has been observed. In the current extensive investigation of the uranium(IV) oxide–bismuth(III) oxide system, this behaviour of the lattice parameter evolution with composition has been confirmed and its origin identified. Even under inert atmosphere at 800 °C, UIV oxidises to UV/UVI as a function of the substitution degree. Thus, using a combination of three methods (XRD, XANES and Raman) we have identified the formation of the BiUVO4 and Bi2UVIO6 compounds, within this series. Moreover, we present here the Rietveld refinement of BiUVO4 at room temperature and we report the thermal expansion of both BiUVO4 and Bi2UVIO6 compounds.