Heat Capacity and Enthalpy of LaNi5 in the Temperature Range 57–1542 K

We have studied the heat capacity and enthalpy of LaNi₅ at low and high temperatures. Based on low-temperature measurements of the heat capacity, we have calculated the values of the enthalpy, entropy, and reduced Gibbs energy of the intermetallic under standard conditions. We have determined the temperature dependences of the thermodynamic functions for LaNi₅ in the temperature range from 298.15 K to 1542 K.     

Thermodynamic Properties of NdSi1.8 and SmSi2 over a Wide Temperature Range

The heat capacity and enthalpy of NdSi_1.8 and SmSi₂ were investigated in the range 55-2122 K for the first time. The temperature, enthalpy and entropy of the polymorphic transformations and melting of the compounds were determined. The temperature dependencies of the principal thermodynamic functions were established, and are recommended for practical application.     

High-temperature thermodynamic characteristics of Ho5Ge3

The enthalpy of Ho₅Ge₃ is measured by drop calorimetry between 463 and 2314 K for the first time. The temperature dependences of enthalpy, heat capacity, entropy, and Gibbs free energy are plotted and, enthalpy and entropy of melting are calculated.     

Thermodynamic Properties of NdSi1.8 and SmSi2 over a Wide Temperature Range

The heat capacity and enthalpy of NdSi_1.8 and SmSi₂ were investigated in the range 55-2122 K for the first time. The temperature, enthalpy and entropy of the polymorphic transformations and melting of the compounds were determined. The temperature dependencies of the principal thermodynamic functions were established, and are recommended for practical application.

     

Heat Capacity and Enthalpy of Lu5Ge3 at 57-2355 K

The thermal capacity and enthalpy of Lu₅Ge₃ have been examined over a wide temperature range. Low-temperature thermal-capacity measurements have been used to calculate the enthalpy, entropy, and reduced Gibbs energy of the germanide under standard conditions. The coefficients in the temperature dependence of the thermodynamic functions have been determined for the interval 298.15-2355 K. The melting point and enthalpy and entropy of melting of the compound have been determined.     

Heat Capacity and Enthalpy of Bi2Si3 and Bi2Te3 in the Temperature Range 58-1012 K

We have studied the heat capacity and enthalpy of Bi₂Si₃ and Bi₂Te₃ at low and high temperatures. Based on low-temperature measurements of the heat capacity, we have calculated the enthalpy, entropy, and reduced Gibbs energy of the compounds under standard conditions. We have determined the temperature dependences of the thermodynamic functions of Bi₂Si₃ and Bi₂Te₃ in the range 298.15-968 K and 298.15-874 K, respectively. We have determined the melting points and the enthalpies and entropies of melting for the compounds.     

Thermodynamic properties of tungsten diselenide in a broad temperature range

Conclusions The specific heat and enthalpy of 2H-W_1.0.3 Se_2.0 were measured for the first time in the 60–1700 K temperature range. Standard values of enthalpy, entropy, and reduced Gibbs energy of tungsten diselenide were obtained on the basis of low temperature measurements of specific heat. The coefficients of the temperature relationships of the thermodynamic functions of the investigated compound in the 298.15–1800 K range were calculated.The specific heat and enthalpy of the compound steadily increase in the whole investigated temperature range. In the high temperature area the enthalpies of isostructural diselenides of molybdenum and tungsten are equal within the limits of measurement error, which is related to the approximately equal values of the elastic constants of these substances.Deceased.Translated from Poroshkovaya Metallurgiya, No, 5(329), pp. 53–56, May, 1990.     

Thermodynamic properties of calcium hexaboride

The temperature dependence of the heat capacity of CaB₆ in the range 20–2500 K was calculated. The calculated results were confirmed by experimental measurements in the range 198–673 K, and standard enthalpy and entropy values were calculated. A recommended standard enthalpy of formation of CaB₆ was obtained from data in the literature. Equations for the thermodynamic functions of CaB₆ in the range 298.15–2500 K were obtained, which are suitable for the thermodynamic analysis of processes involving calcium hexaboride. Institute for Materials Science Problems, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 7–8, pp. 63–66, July–August, 1997.     

Thermodynamic Properties of the Quasibinary System Bi2Se3 - Bi2Te3 over a Broad Temperature Range

We have studied the heat capacity and enthalpies of solid solutions in the quasibinary system Bi₂Se₃ - Bi₂Te₃ at low and high temperatures. Based on low-temperature measurements of the heat capacity, we have calculated the values of the enthalpy, entropy, and reduced Gibbs energy of the compounds under standard conditions. We have determined the temperature dependences of the thermodynamic functions for the solid solutions Bi₂Se₃ - Bi₂Te₃ (50, 70, and 80 mole% Bi₂Te₃) in the temperature range 298.15 K - T_mp. __________ Translated from Poroshkovaya Metallurgiya, Nos. 7–8(444), pp. 80–85, July–August, 2005.     

Solubility and thermodynamic properties of Y2O3 in LiF-YF3 melts

A systematic investigation was undertaken to measure the solubility of Y₂O₃ in several LiF-YF₂ melts, with the YF₃ composition ranging from 20 to 50 mole pct, in the temperature range of 998 to 1273 K. Experimental results showed that the solubility of Y₂O₄ in the melts increased with increase in temperature and also with increased YF₃ content. The activity of Y₂O₃ was calculated using the free energy of fusion of Y₂O₃, . The was deduced from the values of enthalpy, heat of fusion, and melting point of Y₂O₃. From the known values of activity, the activity coefficients of Y₂O₃ as a function of temperature and melt composition were calculated. Considering the ionic nature of the melt, activity coefficients were also calculated using Temkin’s ideal mixing and electrically equivalent fraction methods. The thermodynamic data, such as integral molar enthalpy, entropy, and free energy of formation, were calculated as a function of composition and temperature. The calculated thermodynamic data showed that the melt exhibited a negative deviation from ideal conditions.     

Heat Capacity of Gadolinium Germanides at Low Temperatures

We have studied the heat capacity of Gd₅Ge₃, GdGe, GdGe_1.5 for the first time by the adiabatic method at temperatures of 55 K to 300 K. Using low-temperature measurements, we have calculated the values of the enthalpy, the entropy, and the reduced Gibbs energy of the germanides under standard conditions.     

Thermodynamic properties of holmium monogermanide

The heat capacity and enthalpy of HoGe is investigated for the first time over a temperature range between 51.62 and 2096 K. The values of heat capacity, entropy, reduced Gibbs energy (J · mole^?1 × × K^?1), and enthalpy (J · mole^?1) are determined at 298.15 K: C °_P(T) = 49.63 ± 0.20; S °(T) = 89.1 ± 0.7; Φ′(T) = 50.9 ± 0.8; H °(T) ? H °(0 K) = 11391 ± 57. Temperature dependences of enthalpy (J · mole^?1) for holmium monogermanide are determined as follows: H °(T) ? H °(298.15 K) = 8.474 × × 10^?3 · T² + 47.13 · T + 226747 · T^?1 ? 15565 and H °(T) ? H °(298.15 K) = 88.91 · T ? 26507, for 298.15–1765 K and 1951–2096 K, respectively. The enthalpy and entropy of HoGe melting are calculated: T_m = 1765 ± 35 K, ΔH_m = 36.3 ± 2.9 kJ · mole^?1, ΔS_m = 20.5 ± 1.6 J · mole^?1 · K^?1.     

Thermodynamic properties of LuGe1.5 at 55 to 1790 K

Adiabatic calorimetry and mixing are used to examine the LuGe_1.5 heat capacity and enthalpy over a wide temperature range for the first time. Standard values and temperature dependences of the main thermodynamic functions are calculated and the enthalpy and entropy of polymorphic transformations and melting of LuGe_1.5 are determined. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 7–8 (456), pp. 76–81, 2007.     

Thermodynamic analysis of the In-Ga-Sb system

The phase diagram and thermodynamic data for the In-Ga-Sb system are fit with a model for the III-V liquid phases, in which the enthalpy and excess entropy of mixing are quartic functions of the atomic fraction and the enthalpy of mixing is a quadratic function of temperature. The Gibbs energy, enthalpy, and entropy of formation of the III-V compounds are obtained as functions of temperature from the heat capacities and the standard enthalpy and entropy of formation at 298 K. The fits are quantitatively satisfactory and better than any hitherto obtained, particularly for the III-V liquidus lines and the ternary liquid. The partial pressures of Sb₂ and Sb₄ are calculated along the three phase curves of In_1-uGa_uJSb(s), and relations given to obtain the relative chemical potentials of In and/or Ga are from these. The enthalpy of mixing of the III-V liquids is calculated for a few hundred degrees above the compound melting points, where presently there are no data. Characteristics of an improved model are postulated.     

The thermal capacity and enthalpy of gadolinium sesquiselenide over a wide temperature range

Measurements have been made on the thermal capacity of γ-Gd₂Se₃ at 58.88–298.34 K. Values have been obtained for the thermal capacity, entropy, reduced Gibbs energy, and enthalpy under standard conditions: C°_p = 125.87 ± 0.5 J· mole⁻¹ · K⁻¹; S°(298.15 K) = 196.5 · 1.6 J · mole⁻¹ · K⁻¹; Φ°(298.15 K) = 103.6 ± 1.6 J · mole⁻¹ · K⁻¹; H°(298.15 K)-H°(0) = 27681 ± 138 J · mole⁻¹. The enthalpy of Gd₂Se₃ has been measured and the major thermodynamic functions have been calculated for the solid and liquid states over the temperature range 450–2300 K. The temperature dependence of the enthalpy in the ranges 300–1800 K and 2000–2300 K are represented: H°(T)-H°(298.15 K) = = 1.1949 · 10⁻² · T² + 122.38 · T + 347402 · T⁻¹ − 38716 and H°(T)-H°(298.15 K) = 262.81 · T-− 196047, respectively. The calculated temperature, enthalpy, and entropy of melting for Gd₂Se₃ are: T_m = 1925 ± 40 K, Δ_mH° (Gd₂Se₃) = 68.5 kJ · mole^-1, Δ_mS°(Gd₂Se₃) = 35.6 J · mole⁻¹ · K⁻¹. __________ Translated from Poroshkovaya Metallurgiya, Nos. 3–4(448), pp. 56–61, March–April, 2006.     

Variation of the partial thermodynamic Properties of Oxygen with Composition in YBa2Cu3O7-δ

The variation of equilibrium oxygen potential with oxygen concentration in YBa₂Cu₃O_7-δ has been measured in the temperature range of 773 to 1223 K. For temperatures up to 1073 K, the oxygen content of the YBa₂Cu₃O_7-δ sample, held in a stabilized-zirconia crucible, was altered by coulometric titration. The compound was in contact with the electrolyte, permitting direct exchange of oxygen ions. For measurements above 1073 K, the oxide was contained in a mag- nesia crucible placed inside a closed silica tube. The oxygen potential in the gas phase above the 123 compound was controlled and measured by a solid-state cell based on yttria-stabilized zirconia, which served both as a pump and sensor. Pure oxygen at a pressure of 1.01 × 10⁵ Pa was used as the reference electrode. The oxygen pressure over the sample was varied from 10^-1 to 10⁵ Pa. The oxygen concentrations of the sample equilibrated with pure oxygen at 1.01 × 10⁵ Pa at different temperatures were determined after quenching in liquid nitrogen by hydrogen reduction at 1223 K. The plot of chemical potential of oxygen as a function of oxygen non- stoichiometry shows an inflexion at δ ～ 0.375 at 873 K. Data at 773 K indicate tendency for phase separation at lower temperatures. The partial enthalpy and entropy of oxygen derived from the temperature dependence of electromotive force (emf ) exhibit variation with compo- sition. The partial enthalpy for δ = 0.3, 0.4, and 0.5 also appears to be temperature dependent. The results are discussed in comparison with the data reported in the literature. An expression for the integral free energy of formation of YBa₂Cu₃0_6.5 is evaluated based on measurements reported in the literature. By integration of the partial Gibbs’ energy of oxygen obtained in this study, the variation of integral property with oxygen concentration is obtained at 873 K.     

Thermodynamic description of Sn-Y and Mg-Sn-Y systems

The thermodynamic optimization of the Sn-Y and Mg-Sn-Y systems was critically carried out by means of the CALPHAD（CALculation of PHAse Diagram） technique. In the Sn-Y system, the solution phases（liquid, bcc, bct and hcp） were described by the substitutional solution model. The compound Sn3Y5, which has a homogeneity range, was treated as the formula（Sn, Y）3（Sn, Y）2Y3 by a three-sublattice model in accordance with the site occupancies. In the Mg-Sn-Y system, the liquid phase was treated as the formula（Mg, Sn, Y, Mg2Sn） using an associated solution model, and bcc, bct and hcp were treated as the formula（Mg, Sn, Y）. The compound Sn3Y5 was treated as the formula（Sn, Y, Mg）3（Sn, Y, Mg）2Y3. The ternary compound MgSnY was treated as stoichiometric compound. A set of self-consistent thermodynamic parameters of the Mg-Sn-Y system was obtained. The projection of the liquidus surfaces and the reaction scheme of the Mg-Sn-Y system were predicted.     

Nitrogen solubility in liquid Fe-Ta,Fe-Cr-Ta,Fe-Ni-Ta,and Fe-Cr-Ni-Ta alloys

The nitrogen solubility in liquid Fe-Ta, Fe-Cr-Ta, Fe-Ni-Ta, and Fe-18 pet Cr-8 pet Ni-Ta alloys was measured using the Sieverts’ method. The experiments covered the temperature range from 1782 to 2031 K, and tantalum contents from 2.0 to 20.0 wt pct Ta. Nitrogen solution obeyed Sieverts’ law and no nitride precipitation was observed in this concentration range. Tantalum increases the nitrogen solubility and the heat of solution of nitrogen is more negative at higher tantalum contents in these alloys. The excess enthalpy and entropy of solution of nitrogen were determined. The first and second order interaction parameters between nitrogen and tantalum were determined as a function of temperature, e _N ^Ta = -101.7/T + 0.018 and e _N ^TaTa = -3.27/T + 0.0022. The effects of alloying elements on the activity coefficient of nitrogen were measured and the second order cross-interaction parameters between nitrogen and Ta with Cr and Ni were determined at 1873 K as e _N ^CrTa = 0.00052 and e _N ^NiTa = 0.00045.     

Thermodynamic properties of praseodymium germanides in the range 55–1940 K

The heat capacity and enthalpy of Pr₅Ge₃, PrGe, and PrGe_1.8 were investigated over a wide temperature range for the first time. The temperatures, enthalpies, and entropies of melting of these compounds, and of the polymorphic transformation in PrGe_1.8 were determined. Temperature dependencies of the basic thermodynamic functions were calculated and are recommended for practical use. Translated from Poroshkovaya Metallurgiya, Nos. 5–6(413), pp. 54–60. May–June, 2000.