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

Abstract In the Na–U–Mo–O system, five compounds with composition Na 2 UMo 2 O 10 , Na 2 U 2 Mo 2 O 13 , Na 2 U 2 Mo 3 O 16 , Na 2 UMo 4 O 16 and Na 2 U 2 Mo 4 O 19 were prepared by solid state reaction of Na 2 MoO 4 , UO 3 and MoO 3 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 Na 2 U 2 O 7 . Infrared spectra of all the compounds show strong spectral bands in the range 700–950 cm −1 due to MoO 4 - 2 tetrahedra and the UO 2 2 + group. A pseudo-ternary phase diagram of Na 2 O–UO 3 –MoO 3 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.