Abstract
Heat-capacity measurements by adiabatic equilibrium calorimetry are reported for y-phase Pr2S3, Tb2S3, and DY2S3 between 5 and 350 K. Highly purified samples were prepared and their composition verified by chemical analysis. Precision lattice parameters were determined for each compound and are compared with literature values. The total heat capacity has been resolved into lattice, magnetic, and Schottky components by a volumetric approach. The experimental Schottky contributions accord with the calculated curves based on the crystal field splitting of the 2S+ ILJ ground state of the lanthanide ions occupying sites ofS4 symmetry in the Th3P 4 lattice. The individual crystal-field electronic energy levels have been obtained in part from an analysis of the hot-band data observed in the absorption spectra ofPrzS3, Tb2S3 , and DY2S3' and from a calculated splitting in which the crystal-field parameters Bkm , were determined from a lattice-sum calculation. Molar thermodynamic properties are reported for all three compounds. The entropy at 298.15 K {SO - SO (7 K)}, is 22.78R, 22.93R, and 23.36R, for y-phase Pr2S3' Tb2S3 , and DY2S3' respectively.
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