High-temperature heat capacities of EuPO4 and SmPO4 synthetic monazites

High-temperature enthalpy increments of monazite-type EuPO4 and SmPO4 were measured by drop calorimetry in the temperature range 450–1570 K and the heat capacity was derived. The excess heat capacity Cexs was calculated by subtracting the lattice heat capacity, interpolated from isostructural LaPO4 (4f0) and GdPO4 (4f7) compounds. A good agreement was found with Cexs calculated from (estimated) crystal field energies. The heat capacity of PrPO4 was estimated with this approach.