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.