X-ray and thermal studies of the Na-U-Mo-O system

In the Na-U-Mo-O system, five compounds with composition Na2UMo2O10, Na2U2Mo2O13, Na2U2Mo3O16, Na2UMo4O16 and Na2U2Mo4O19 were prepared by solid state reaction of Na2MoO4, UO3 and MoO3 in the required stoichiometric ratio. The compounds were characterized by X-ray powder diffraction, infrared and thermal analysis techniques. The XRD data of all the above-mentioned compounds were indexed on the orthorhombic system. All the compounds showed thermal stability up to 600 °C in air and decomposed at 950 °C to form Na2U2O7. Infrared spectra of all the compounds show strong spectral bands in the range 700-950 cm−1 due to MoO4-2 tetrahedra and the UO22+ group. A pseudo-ternary phase diagram of Na2O-UO3-MoO3 was drawn using the quaternary compounds and information available on Na-U-O, Mo-U-O and Na-Mo-O ternary systems. The various phase fields prepared during this work were established by XRD analysis.