The thermodynamics of perchlorates. I. Heat capacity of ND4ClO4 from 7 to 345 K and the analysis of heat capacities and related data of NH4ClO4 and ND4ClO4

The heat capacity of the orthorhombic salt: deuterated ammonium perchlorate, ND4 ClO4 , was measured from 7 to 345 K using adiabatic calorimetry. The heat capacity against temperature curve is smooth, continuous and without anomaly. Values of the standard molar thermodynamic quantities are presented up to 340 K. The heat capacities of ND4 ClO4 and NH4 ClO4 have been analyzed. The contributions to the vibrational heat capacity from the external optical modes of NH+4 or ND+4, ClO−4 and libration from the external modes of ClO−4 along with those of vibration from the internal optical modes of NH+4 or ND+4 and ClO−4, and the acoustic lattice modes for these ions have been calculated. The difference between the experimental and calculated heat capacity, called the residual heat capacity, equals the contribution from ammonium ion rotation and the thermal expansion of the lattice. With recent thermal expansion data, the correction from constant stress to constant strain has been applied and the derived rotational heat capacities of the NH+4 and ND+4 are determined to be in qualitative agreement with those derived from various rotational models.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70290/2/JCPSA6-91-1-399-1.pd

Uranium Monosulfide. The Ferromagnetic Transition. The Heat Capacity and Thermodynamic Properties from 1.5° to 350°K

The heat capacity of uranium monosulfide was measured from 1.5° to 22°K by an isothermal (isoperibol) method and from 6° to 350°K by an adiabatic technique. The ferromagnetic transition at 180.1°K has a characteristic lambda shape and associated magnetic ordering entropy and enthalpy increments of 1.62 ± 0.2 cal °K−1mole−1 and 231 ± 20 cal mole−1, respectively, over the temperature range 0° to 230°K. The correlation of the thermal data with magnetic studies is discussed. The heat capacity below 9°K is represented by Cp  =  5.588 × 10−3T + 2.627 × 10−4T3 / 2 + 6.752 × 10−5T3cal°K−1mole−1Cp=5.588×10−3T+2.627×10−4T3∕2+6.752×10−5T3cal°K−1mole−1, in which the successive terms represent conduction electronic, magnetic, and lattice contributions. Values of the entropy [S°], enthaply function [(H° − H°0) / T][(H°−H°0)∕T], and Gibbs‐energy function [(G° − H°0) / T][(G°−H°0)∕T] are 18.64 ± 0.005, 8.94 ± 0.002, and − 9.70 ± 0.02 cal °K−1 mole−1, respectively, at 298.15°K. The Gibbs energy of formation at 298.15°K is − 72.9 ± 3.5 kcal mole−1.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70623/2/JCPSA6-48-1-155-1.pd

The thermodynamics of ammonium scheelites. III. An analysis of the heat capacity and related data of deuterated ammonium perrhenate ND4ReO4

An analysis of the heat capacity of deuterated and undeuterated NH4ReO4 has been carried out in which the effects of the anisotropy of the thermal expansion have been considered, an approach hitherto not used for ammonium compounds. In the ammonium scheelites, the axial thermal expansion coefficients are very large, but of opposite sign, and as a result the volume of the scheelite lattice is nearly independent of temperature. It is shown that the correction from constant stress to constant strain results in a major contribution to the heat capacity of this highly anisotropic lattice. The difference between the experimental and calculated values of heat capacity, referred to as ΔCp, is expressed as the sum of the contributions from the anisotropy and the rotational heat capacity. The results of the analysis show that the rotational contribution is much smaller then previously thought. However, the exact contribution of the anisotropy cannot be calculated at this time because the elastic constants are not known. In calculating the heat capacity, maximum use has been made of external optical mode frequencies derived from spectroscopic measurements.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71156/2/JCPSA6-85-10-5963-1.pd

Schottky levels and thermodynamic contributions of light lanthanide sesquisulfides having the Th3P4 structure

Heat capacity measurements were made by adiabatic calorimetry over the range 7-350 K on [gamma] phase preparations of four lanthanide sesquisulfides, and the heat capacities were resolved into lattice, magnetic, Schottky and other components. The entropy at 298.15 K for La2S3 which is written as S[deg]/R is 19.51 while values of S[deg] -- S[deg](7 K) for Ce2S3, Nd2S3, Gd2S3 and Dy2S3 are 21.34, 22.38, 20.05 and 22.58 respectively. IR and visible optical spectra of La2S3, Ce2S3, Nd2S3 and Dy2S3 and lattice sum crystal field splitting calculations for Nd2S3, Ce2S3 and Dy2S3 are compared with Raman scattering data and Schottky contributions derived from calorimetry.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25086/1/0000517.pd

The heat capacity and derived thermophysical properties of the high TC superconductor YBa2Cu3O7−δ from 5.3 to 350 K

The heat capacity of the perovskite high‐TC superconductor YBa2Cu3O7−δ was measured from 5.3 to 350 K in an adiabatic calorimetric cryostat. A break in the heat‐capacity curve, associated with the critical temperature for superconductivity was observed between 90.09 and 92.59 K. The transition temperature was identified as 91.44 K, and ΔCp,m was calculated to be 0.559R at that temperature. The lattice heat capacity was evaluated by means of the recently developed Komada/Westrum phonon distribution model and the apparent characteristic temperature ΘKW was calculated to be 107.7 K. The excess electronic heat capacity for the superconducting phase was evaluated and the energy gap was identified as 234. R K. Excess contribution, resulting from magnetic impurities, was noted below 20 K. Thermodynamic properties at selected temperatures are presented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71226/2/JCPSA6-92-11-6794-1.pd

Heat capacity and other thermodynamic properties of CoTe 2 from 5 to 1 030 K and of CoTe 2.315 from 300 to 1 040 K

The heat capacity of orthorhombic (marcasite-type structure) cobalt ditelluride has been measured from 5 to 1 030 K by adiabatic-shield calorimetry with alternate energy inputs and equilibrations. Above 900 K a marked increase in heat capacity occurs which probably signals a change in the composition of the CoTe 2 -phase towards higher tellurium content. Values at 298.15 and 1 000 K in J K −1 mol −1 of the heat capacity ( C p,m ), entropy [ S m ° (T) − S m ° (0)], and Gibbs energy function − [ G m ° (T) − H m ° (0)] T −1 are 75.23, 114.5, 49.93, and 132.4, 216.2, 139.17, respectively. Consistent with the metallic behavior of CoTe 2 , deviation of the heat capacity from the Debye T 3 -law was found at low temperatures. Comparison with the heat capacity of FeTe 2 shows a Schottky -like deviation with a maximum of 7.3 J K −1 mol −1 at 80 K and evidences the influence of the additional 3 d-electron in cobalt compared to iron. Heat capacity measurements were made on CoTe 2.33 to ascertain the existence range of the CoTe 2+ x -phase and the entropy of the associated structural disorder. Es wurde die Wärmekapazität des orthorhombischen Kobaltditellurids (Markasit-Typ) zwischen 5 und 1 030 K mittels adiabatisch abgeschirmter Kalorimetrie mit alternierender Energiezufuhr und Gleichgewichtseinstellung gemessen. Über 900 K tritt ein deutlicher Anstieg der Wärmekapazität ein, der möglicherweise einen Wechsel in der Zusammensetzung der CoTe 2 -Phase zu einem höheren Tellur-Gehalt anzeigt. Entsprechende Werte bei 298.15 bzw. 1 000 K in J K −1 mol −1 für die Wärmekapazität ( C p, m ), die Entropie [ S m ° (T) − S m ° (0)] und die Gibbs Energiefunktion − [ G m ° (T) − H m ° (0)] T −1 sind 75.23, 114.5, 49.93 bzw. 132.4, 216.2, 139.17. In Übereinstimmung mit dem metallischen Verhalten von CoTe 2 wurde bei niedrigen Temperaturen eine Abweichung der Wärmekapazität vom Debye 'schen T 3 -Gesetz gefunden. Ein Vergleich mit der Wärmekapazität von FeTe 2 zeigt eine Schottky -gemäße Abweichung mit einem Maximum von 7.3 J K −1 mol −1 bei 80 K; dies zeigt den Einfluß der zusätzlichen 3 d-Elektronen im Kobalt, verglichen mit Eisen. Es wurden Wärmekapazitätsmessungen an CoTe 2.33 durchgeführt, um den Existenzbereich der CoTe 2+ x -Phase und die Entropie der damit zusammenhängenden strukturellen Unordnung zu ermitteln.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41694/1/706_2004_Article_BF00810867.pd

Recent thermochemical research on reactor materials and fission products

By adiabatic calorimetric measurements from 5 to 350 K and enthalpy increment determinations above the ambient temperature the thermophysical properties of such uranium compounds as UF3, UC13, UBr3, URu3, URh3, UPd3 and fission product combinations such as RuO2, RuSe2, and CsBO2 have been obtained. In addition, the enthalpies of formation of these substances have been determined by EMF and enthalpy of solution measurements. By combining these measurements the formation properties have been derived as a basis for modeling, critical evaluation and prediction. Some examples of these applications are given.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27772/1/0000166.pd

The thermochemical and thermophysical properties of Cs2RuO4 and Cs2MnO4 at temperatures from 5 K to 1000 K

Low-temperature heat capacities from 5 K to 350 K by adiabatic calorimetry and high-temperature enthalpy increments above T = 450 K to 800 K by drop calorimetry of Cs2RuO4 and Cs2MnO4 have been measured. The two compounds exhibit solid-to-solid phase transitions at T = 906.8 K and T = 1051.9 K, respectively, and melt at T = 1211.8 K and T = 1175.5 K, respectively. The enthalpies of transition and the melting temperatures have been determined by d.s.c. measurements. From the results, smoothed thermochemical and thermophysical functions have been tabulated at selected temperatures up to 1000 K. For the standard molar entropies of Cs2RuO4 and Cs2MnO4 at T = 298.15 K the values Som/R = 31.64 and 28.77, respectively, have been found.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29933/1/0000290.pd

Heat capacity and thermodynamic properties of synthetic heazlewoodite, Ni3S2, and of the high-temperature phase Ni3±xS2

The heat capacity of synthetic heazlewoodite (Ni3S2) was measured over the temperature range 5 K to 350 K by equilibrium adiabatic calorimetry and compared with earlier results. High-temperature results on this phase and on (two-phase) Ni2.9S2 were obtained through the transition regions and up to about 1000 K. In addition to comparing the post-(834 K)-transitional heat capacity with that of fast ionic conductors it is discussed phenomenologically with Helmholtz-energy modelling for the phase transformation. Thermodynamic functions have been evaluated and selected values are, for R = 8.3144 J·K-1·mol-1:Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29536/1/0000624.pd

The thermodynamic properties of cesium metaborate CsBO2 from 5 to 1000 K

The low-temperature heat capacities of cesium metaborate were measured by adiabatic calorimetry from 9 to 346 K. High-temperature enthalpy increments of CsBO2 were measured by drop calorimetry from 414 to 671 K. In addition, the melting data were measured by DSC. The thermodynamic functions CpXXX(T), SXXX(T), {HXXX(T)-HXXX(298.15 K)}, [Delta]fHXXX(T) and [Delta]fGXXX(T) were calculated up to the melting point.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27264/1/0000274.pd