Correlation of spectral and heat-capacity Schottky contributions for Dy2O3, Er2O3, and Yb2O3

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Abstract
A self‐consistent interpretation of the Raman and infrared spectra and the heat‐capacity measurements on Dy2O3, Er2O3, and Yb2O3, which have the cubic (bixbyite) structure, is presented. New spectra recorded at 10, 80, and 300 °K on oriented single crystals of each oxide are compared with published spectral data and interpretations. Most of the data are consistent with earlier interpretations. However, several additional crystalline–electric‐field split levels have been found for ions in the C3i sites that, together with the established CEF‐split levels for ions in the C2 sites, now provide a total picture for the CEF splitting of the ground‐state manifolds. These values allow calculation of the total Schottky contribution to the heat capacity. Experimental Schottky heat‐capacity values are independently derived by the volume‐weighted lattice‐contribution scheme. Correlation between optical data and heat‐capacity measurements is found to be excellent. Further confirmation of the analysis is found in the agreement (to within 3%) between observed and calculted CEF splitting for the lanthanide ions on C2 sites.