LAUSR

Abstract Compounds SrU(PO 4 ) 2 (SUP) and BaU(PO 4 ) 2 (BUP) were synthesized by solid state method in high purity argon atmosphere at 1473 K. Structures of both the compounds were derived using Rietveld method from powder X–ray diffraction (XRD) data. Compound SUP is orthorhombic and has ordered cheralite type structure with alternate layers of SrO 10 and UO 8 polyhedra. Compound BUP is monoclinic and has a non cheralite structure with Ba and U in 14 and 8 coordinations, respectively. Thermogravimetric (TG) curves obtained by heating both the compounds in air confirm the oxidation of U(IV) to U(VI) between 600 and 1573 K. High temperature XRD data collected in vacuum up to 1473 K indicated positive thermal expansion for both the compounds. Heat capacity (C p ) measurements were also carried out for both the compounds by heat flow Differential Scanning Calorimeter (DSC) in argon atmosphere from 300 to 873 K.