Thermophysics of the lanthanide trihydroxides IV. The heat capacity of Ho(OH)3 from 11 to 350 K. Lattice and Schottky contributions

Abstract

From values of the heat capacity of microcrystalline Ho(OH)3 determined by precise adiabatic calorimetry from 11 to 350 K, the Schottky contribution associated with the Stark splitting of the ground J-manifold (5I8) was resolved by means of an extrapolation of the known lattice heat-capacity variation between La(OH)3 and Gd(OH)3. This calorimetrically deduced Schottky contribution is compared with that calculated from spectroscopically derived energy levels of Ho3+ doped Y(OH)3. Because the lattice parameters of Y(OH)3 and Ho(OH)3 are nearly identical it is assumed that the electronic energy levels of the Ho3+ ions are the same in either host lattice. These results together with independent heat-capacity measurements made at lower temperatures were used to adjust the low-temperature thermophysical functions to evaluate Cp/R, So/R, and -["Go - Ho(0)'/RT], at 298.15 K as 13.80, 15.64, and 7.855.