Low-temperature heat capacities, thermophysical properties, optical spectra, and analysis of Schottky contributions to Pr(OH)3

Abstract

From values of the heat capacity of microcrystalline Pr(OH)3 determined by precise adiabatic calorimetry from 15 to 350 K, the Schottky contribution associated with all but the lowest Stark level was resolved with the aid of a model of the lattice heat capacity based upon the molar volumes of the lanthanide trihydroxides. Visible and infrared absorption spectra were taken at approximately 95 K on microcrystalline mulls and the energy-level scheme and crystalline electric-field parameters evaluated. The Schottky contribution of all levels above the first excited state ([mu] = 3) was resolved by a new scheme for modeling the lattice contribution and compared with the same contribution deduced from the spectral results. Excellent accord was observed. These results together with magnetic results and the first excited Stark level were used to adjust the low-temperature heat capacities and thermodynamic functions so as to evaluate Cp/R, So/R, and - {Go - Ho(0)}/RT, at 298.15 K as 14.154, 15.84, and 7.766, respectively.