The low-temperature heat capacity of CaUO4 and SrUO4

The heat capacity of calcium monouranate CaUO4 and strontium monouranate SrUO4 have been measured over the temperature range (2 to 300) K. The results are significantly different from earlier measurements, confirming the conclusions from our previous study on BaUO4. The standard entropy at T = 298.15 K of orthorhombic α-SrUO4 is consistent with the values for the isostructural BaUO4 as well as the alkali uranates Na2UO4 and Cs2UO4. The standard entropy of the rhombohedral CaUO4 is appreciably different, which is attributed to the different structures of the uranium sublattices.