Robert D. Chirico

Thermophysics of the lanthanide trihydroxides II. Heat capacities from 10 to 350 K of Nd(OH)3 and Tb(OH)3. Lattice and Schottky contributions

Abstract Heat capacities have been measured from near 7 to 350 K for Nd(OH) 3 and Tb(OH) 3 and the derived thermophysical properties evaluated using previously reported heat capacities at lower temperatures. At 298.15 K the values of C p R , S o R , and −{G c − H o (0)} RT are 14.15, 15.62, and 7.484 for Nd(OH) 3 and 13.72, 15.44, and 7.525 for Tb(OH) 3 . The resolution of the lattice and Schottky contributions for both compounds is discussed. The Tb(OH) 3 calorimetric Schottky contribution is correlated with spectroscopically deduced energy levels for Tb(OH) 3 and Tb 3+ -doped Y(OH) 3 , while that of Nd(OH) 3 is used to estimate the crystal-field splitting of the 4 I 9 2 J -manifold. The effect of temperature upon the Schottky heat capacities is discussed.

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

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 (μ = 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 CpR, SoR, and − {Go − Ho(0)}RT, at 298.15 K as 14.154, 15.84, and 7.766, respectively.

Thermophysics of the lanthanide hydroxides I. Heat capacities of La(OH)3, Gd(OH)3, and Eu(OH)3 from near 5 to 350 K. Lattice and Schottky contributions☆

From values of the heat capacity of microcrystalline La(OH)3, Gd(OH)3, and Eu(OH)3 determined by precise adiabatic calorimetry from near 10 to 350 K, the Schottky contribution associated with the low-lying J-manifolds of Eu(OH)3 was resolved with the aid of a new lattice-heat-capacity approximation based upon volumetric interpolation between the lattice heat capacities of the La(OH)3 and Gd(OH)3 homologs. This calorimetrically deduced Schottky contribution to the heat capacity of Eu(OH)3 was compared with the same contribution calculated from spectral data. Excellent accord was observed over the entire temperature range investigated. The experimental heat capacities of this study together with previously published low-temperature (0.45 to 18 K) magnetic and heat-capacity data for Gd(OH)3 permit evaluation of thermophysical functions relative to T = 0 for each compound.

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

A self-consistent interpretation of existing and new Raman- and infrared spectra on oriented single crystals and heat-capacity measurements on Dy2O3, Er2O3, and Yb2O3, which have the cubic (bixbyite) structure is presented.

Thermophysics of the lanthanide trihydroxides III. Heat capacities from 5 to 350 K of the related compound Y(OH)3. Lattice contribution

Abstract Heat-capacity measurements between 5 and 350 K have been performed upon a microcrystalline sample of Y(OH)3. The heat capacities can be represented by a simple sigmate curve; no anomalous behavior was observed. Comparison with previously published results for the iso-anionic compounds La(OH)3 and Gd(OH)3 provides insight into the physical origins of experimentally observed trends in the lattice contributions of lanthanide compounds and suggests a rationale for the volume-weighted lattice-approximation scheme, which has been applied with great success to the lighter lanthanide trihydroxides.

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 C p R , S o R , and −[ “G o − H o (0)’ RT ] , at 298.15 K as 13.80, 15.64, and 7.855.

Thermophysics of the Lanthanide Trichlorides—Reanalysis of the Schottky Heat Capacity Contributions

The heat capacity data on the anhydrous lanthanide trichlorides from 5 to 350 K of Sommers and Westrum provide an excellent opportunity to further test the volumetric lattice heat-capacity approximation method. Schottky contributions in PrCl3, SmCl3, and EuCl3 were calorimetrically derived using the volume-weighted interpolation between the lattice heat capacities of the La and Gd homologs. Previously qualitative agreement had been observed upon comparison of these calorimetrically derived Schottky contributions with those calculated from spectroscopic data obtained for Ln(III) doped LaCl3 crystals. Excellent accord between “spectroscopic” and “calorimetric” Schottky contributions is achieved by adjusting the Stark-level energies to represent those of the concentrated salts through extrapolation of the Ln(III) doped LaCl3 energies to stronger crystal fields either empirically or by means of estimated crystal-field parameters. These methods are described and the resulting energy levels are compared with the spectroscopic data that do exist for the concentrated trichlorides.

Thermophysics of the Lanthanide Trihydroxides — Resolution of the Lattice and Schottky Contributions

Lattice heat capacities and Schottky contributions have been resolved and analyzed for a series of lanthanide trihydroxides through heat-capacity measurements from 5 to 350 K. These compounds all crystallize with the UCl3-type structure and, therefore, are a particularly suitable series for which to attempt this separation.