Phase study in SrO–UO3–MoO3 system

The sub-solidus phase relations in SrO–UO3–MoO3 system were determined at 1023 K in air. Various compounds in SrO–UO3, UO3–MoO3, SrO–MoO3 and Sr–Mo–U–O systems were synthesized by solid state method, reacting SrCO3(s), UO3(s) and MoO3(s) in desired molar proportions at 1023 K. A pseudo-ternary phase diagram of SrO–UO3–MoO3 system was drawn on the basis of phase mixtures obtained in the present work. A single quaternary compound, SrUMo4O16(s) was identified. The compound melts at 1043 K and decomposes above 1173 K to give SrMoO4(s) and U3O8(s). SrUMo4O16 showed positive thermal expansion under vacuum from ambient to 873 K with an average volume expansion coefficient αv = 9.73 × 10−6 K−1. The molar heat capacity of SrUMo4O16(s) was measured using differential scanning calorimeter. Using the thermodynamic data, oxygen, MoO3 and strontium potential diagrams of SrO–UO3–MoO3 system have been computed at 1023 K