Thermodynamic Assessment of the Al-Ba System

The Al-Ba was thermodynamically optimized with the help of CALPHAD method. The solution phases such as liquid, fcc and bcc phases were modeled as substitutional solution phases. The excess Gibbs energies of these phases were treated with Redlich-Kister polynomial functions. A set of self-consistent thermodynamic parameters for describing various phases in the Al-Ba system was obtained, which can well reproduce the corresponding experimental data. The Al-Ba-Ni ternary system were also extrapolated based on the present binary system.     

Thermodynamic Assessment of the Mn-B System

The phase equilibrium and thermodynamic data on the Mn-B system are critically reviewed. Based on the experimental data, a thermodynamic modeling is performed on this system. A set of self-consistent thermodynamic parameters is obtained and the calculated results are in general agreement with the experimental data. A parameter ξ is introduced to compare the degree of flatness of the δMn/L liquidus with those in other metal-boron systems. It is found that the δMn/L liquidus is the flattest, which causes difficulties in its modeling. An effective approach to evaluate the thermodynamic parameters for o-Mn₂B_0.982 phase is developed. Such an approach is valid for evaluating thermodynamic parameters of the phases with limited phase diagram data.     

Thermodynamic Assessment of the Fe-Mn-O System

The C-Cr-Fe-Ni-O system has recently been studied with the intention to thermodynamically describe the influence of oxygen on high alloyed steels. In this study the ternary Fe-Mn-O system is assessed and part of the binary Mn-O system is reassessed. α- and β-hausmannite (Mn₃O₄) were earlier described as stoichiometric phases, but are here described using the compound energy formalism with a four sublattice model to be consistent with the preceding study of the Cr-Fe-Ni-O spinel. The liquid phase is assessed using the ionic two-sublattice model. Good agreement between calculated and experimental values is achieved.     

Thermodynamic Assessment of Dy-Co System

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Thermodynamic Assessment of Co-Y System

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Thermodynamic Assessment of Fe-Dy System

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Thermodynamic Assessment of the Ru-Zr Binary System

The Ru-Zr system has been assessed by means of the Calphad approach. The solution phases (Liquid, (Ru), and were modeled with the sublattice formalism and the excess term of the Gibbs energy with the Redlich-Kister equation. The intermetallic compounds and RuZr, which have homogeneity ranges, were treated as the formula and by a two-sublattice model with a mutual substitution of Ru and Zr on both sublattices. The calculated phase diagram and the thermodynamic properties of the system are in satisfactory agreement with the experimental data.     

A Thermodynamic Assessment of the Li-Ge System

The thermodynamic modeling of the Li-Ge binary system was carried out using CALPHAD (CALculation of PHAse Diagram) method. The liquid phase was described as substitutional solution phase, while the nine intermetallic compounds Li₁₇Ge₄, Li_4.1Ge, Li₁₅Ge₄, Li₁₃Ge₄, Li₁₄Ge₆, Li₉Ge₄, Li₁₂Ge₇, LiGe and Li₇Ge₁₂ were treated as stoichiometric compounds. The temperature dependent interaction parameters \(L_{i}^{\text{Liquid}}\) of liquid were described by either exponential (Kaptay equation) or linear equation, respectively. The comparisons between experimental data and modeled results are given. The calculations based on the obtained thermodynamic parameters are in good agreement with both phase diagram data and thermodynamic values. In particular, the liquid phase was successfully described by the exponential equation for it is possible to avoid the occurrence of the artificial miscibility gap at high temperatures.     

Thermodynamic Assessment of the Fe-Y System

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Thermodynamic Assessment of Zn-Fe-Nb Ternary System

The Nb-Zn binary system has been thermodynamically assessed using CALPHAD approach by combining available experimental data and the data from ab initio calculations of the formation enthalpies for NbZn₂, NbZn₃ and NbZn₁₅. Solution phases including Liquid, Bcc, Hcp were modeled as substitutional phases, of which the excess Gibbs energies being formulated with the Redlich-Kister polynomial function. All the binary compounds were treated as stoichiometric phases. Incorporated with the reported thermodynamic parameters of Fe-Zn and Fe-Nb binary systems, two isothermal sections at 723 and 873 K of Zn-Fe-Nb ternary system were thermodynamically optimized where one stoichiometric ternary phase (τ) and the ternary solubility in intermetallic compound (ε) were taken into consideration. Furthermore, liquidus projection was predicted accordingly.     

Experimental Investigation and Thermodynamic Assessment of the Hf-Mn System

The Hf-Mn binary system was investigated via experiment and thermodynamic assessment. Six alloys, which were prepared by arc melting the elements, were annealed at 1223 K for 240 h or at 923 K for 408 h, followed by analysis using x-ray diffraction, optical microscopy, scanning electron microscopy, and electron probe microanalysis. The homogeneity range of HfMn₂ was determined to be from 66.4 to 73.5 at.% Mn at 1223 K and from 65.3 to 73.0 at.% Mn at 923 K, while that for HfMn was measured to be very limited (48.4-49.0 at.% Mn at 1223 K). The invariant equilibrium of βHf ↔ αHf + HfMn, which was previously proposed to occur at 1123 K, was not observed according to the present differential thermal analysis. The thermodynamic optimization for the Hf-Mn system is then conducted by taking into account the reliable experimental data from the literature and the present work. The calculation using the obtained parameters can reproduce most of the experimental phase diagram data and thermodynamic properties.     

First-Principle Calculation Assisted Thermodynamic Assessment of the Pt-Pb System

Thermodynamic assessment of the Pt-Pb binary system has been performed by combining first-principle calculations with the CALPHAD method. The formation enthalpies of the Pt₃Pb and PtPb₄ were calculated by using the projector-augmented-wave (PAW) method within the generalized gradient approximation (GGA). The CALPHAD assessment of the Pt-Pb system was then performed. The solution phases (liquid and fcc) were treated as substitutional solutions, the excess Gibbs energies of which were modeled using the Redlich-Kister polynomial. The three intermetallic compounds, Pt₃Pb, PtPb, and PtPb₄, were described as stoichiometric phases. Thermodynamic parameters of all the phases were optimized, which reproduces the most experimental data.     

Thermodynamic Assessment of the Ag-Se System Aided by First-Principles Calculations

The substitution of Ag for Cu in CuIn_xGa_1?xSe₂-based photovoltaic absorber layers can be used to adjust the bandgap energy to better optimize the overall cell efficiency. Based on available thermochemical, equilibrium, and structural data, the Ag-Se system has been assessed and modeled. Given the order-disorder structure transition Ag₂Se, the 2- and 3-sublattice models were used to represent the low- and high-temperature phases of the intermetallic compound respectively. Density functional theory based first-principles calculations were used to calculate the Gibbs energy of formation of the end-member compounds. A set of modeling parameters was obtained by the CALculation of PHAse Diagram approach and reasonable agreement was obtained between the experimental thermodynamic properties of the stable phases and the phase relationships in the Ag-Se system.