Thermal expansion studies on Th(MoO4)2, Na2Th(MoO4)3 and Na4Th(MoO4)4

Thermal expansion behavior of Th(MoO4)2, Na2Th(MoO4)3 and Na4Th(MoO4)4 was studied under vacuum in the temperature range of 298–1123 K by high temperature X-ray diffractometer. Th(MoO4)2 was synthesized by reacting ThO2 with 2 mol of MoO3, at 1073 K in air and Na2Th(MoO4)3 and Na4Th(MoO4)4 were prepared by reacting Th(MoO4)2 with 1 and 2 mol of Na2MoO4, respectively at 873 K in air. The XRD data of Th(MoO4)2 was indexed on orthorhombic system where as XRD data of Na2Th(MoO4)3 and Na4Th(MoO4)4 were indexed on tetragonal system. The lattice parameters and cell volume of all the three compounds, fit into polynomial expression with respect to temperature, showed positive thermal expansion (PTE) up to 1123 K. The average value of thermal expansion coefficients for Th(MoO4)2, Na2Th(MoO4)3 and Na4Th(MoO4)4 were determined from the high temperature data.