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

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.