Schottky contribution to the heat capacity of monazite type (La,Pr)PO4 from low temperature calorimetry and fluorescence measurements

Abstract We show that the combination of fluorescence spectroscopy and low temperature heat capacity measurements of Pr-containing samples in the (La, Pr)PO 4 solid solution series can be employed to strongly constrain the Stark energy levels of Pr 3+ in monazite type structures. The resulting set of Stark energy levels for the 3 H 4 ground state of Pr 3+ reproduces the low temperature Schottky anomaly of the heat capacity much more accurately than theoretical models published earlier. We also show that there is no excess heat capacity along the binary solid solution with respect to an interpolation between the two end members LaPO 4 and PrPO 4 .