[en] The vaporization of alloys of the Ni-Hf system was investigated in the temperature range between 1,200 and 1,650 K by Knudsen effusion mass spectrometry. The different compositions of the 16 alloy samples investigated covered the complete homogeneity range of the Ni-Hf system. The partial pressure of Ni was determined over all samples. The thermodynamic activities of Ni and Hf in the alloys were evaluated from these pressures and by Gibbs-Duhem integration. In addition, Gibbs energies of formation, enthalpies of formation, and entropies of formation resulted for the nine intermetallic phases of the Ni-Hf system. Beside similar thermodynamic data for the evaporation reactions were studied. The data obtained are discussed and a method for distinguishing the congruent melting compounds from the peritectic ones by defining stability factors calculated from the Gibbs energies of formation is suggested

[en] A (Knudsen cell + mass spectrometer) has been used to study thermodynamic activities in (xNaI+(1-x)CsI). The mass spectrum of the vapours over the mixture has measured over a temperature interval of 930 to 1050 K. From the ion intensities, thermodynamic activities were calculated by applying the Gibbs-Duhem and monomer-to-dimer ratio technique. The NaI and CsI activities over the full composition range, the excess partial molar and excess molar enthalpies, the corresponding entropy changes, and the excess chemicals potentials and excess molar Gibbs energies are reported. This study yields negative excess molar enthalpies over the whole composition range which, together with the other thermodynamic quantities, indicate deviation of the mixture from ideality; that is, considerable interaction forces exist between NaI and CsI molecules in the melts. (author)

[en] Highlights: • Thermodynamics of the Li–Sn system by Knudsen Effusion Mass Spectrometry. • Vaporization of five liquid binary Li–Sn alloys (x_Li = 0.1; 0.2; 0.3; 0.4 and 0.5). • Vaporization of three solid binary Li–Sn alloys (x_Li = 0.71; 0.76 and 0.81). • Thermodynamic data like activities, mixing enthalpies and entropies were calculated. • Powder XRD measurements were performed to check phase homogeneity of the samples. -- Abstract: The vapourization of five liquid binary Li–Sn alloys (x_Li = 0.1; 0.2; 0.3; 0.4 and 0.5) and three solid binary Li–Sn alloys (x_Li = 0.71; 0.76 and 0.81) was investigated in the temperature range from 648 K to 1014 K by Knudsen Effusion Mass Spectrometry (KEMS). It is the first time that an intensive KEMS investigation was carried out for a wide composition range of this binary system. From the obtained temperature dependence of the thermodynamic activities, thermodynamic properties, such as mixing enthalpies and entropies, were calculated. In addition, sublimation enthalpies for pure lithium, recalculated to 0 K by the enthalpy increment functions of Li(c) and Li(g), demonstrated the stability and accuracy of the experimental setup. The obtained thermodynamic data agree with the corresponding literature data, thus showing the feasibility of this method for determining the thermodynamic data of lithium-ion battery materials

[en] The compound energy formalism is widely used for thermodynamic descriptions of intermediate phases containing vacancies. For a two-sublattice model, represented by (A,B,Va)_0.5:(A,B,Va)_0.5, it is physically necessary to take the reference state Gibbs energy of the pure vacancy end member, G_Va:Va deg., as zero, irrespective of temperature, pressure, or the chemical composition and structure of the actual intermediate phase containing the vacancies. This assumption leads to more than one possible solution for the calculated value of the equilibrium vacancy concentration. The assumption can be avoided if the compound end members are regarded as cluster solution members and an ideal dilute solution reference state is used for the vacancy clusters. In this case, G_Va:Va deg. does depend on the host as well as on temperature and pressure. An analysis of the thermodynamic properties of the B2 phase in the Al-Ni system is used as a demonstration of this alternative view

[en] Highlights: • The experimental KEMS data fit well with the Redlich–Kister sub-regular solution model applied to Li–Sn melt. • The Redlich–Kister binary interaction L-parameters of the Li–Sn melt were provided in this work. • The experimental KEMS data fit well with the ideally associated mixture model, too. • The quantitative associate composition of the Li–Sn melt was given. • The thermodynamic properties of the associate-forming reactions were also provided. - Abstract: The mixing thermodynamic properties of liquid Li–Sn system, determined previously by Knudsen effusion mass spectrometry (KEMS), were successfully fitted to both Redlich–Kister (RK) sub-regular mixture and ideally associated mixture (IAMT) models. The RK binary interaction L parameters, as a function of temperature in the CALPHAD-type functional form, were obtained as follows: L⁽⁰⁾=-(108580±0.00171)+(16.4±1.6·10^-5)·T+(1.96496·10^-9±2.03133·10^-6) ·T·ln(T) L⁽¹⁾=-(96600±4700)+(3.3±43.0)·T+(4.4±5.6)·T·ln(T) L⁽²⁾=-(64670±190)-(44.4±1.7)·T+(8.44±0.22)·T·ln(T) L⁽³⁾=-(20900±1500)-(29±14)·T+(4.3±1.8)·T·ln(T) The former literature data provided only qualitative information on possible liquid associates but no quantitative associate composition was given as a function of the sample composition and temperature. The experimental KEMS data in the composition range X_Li = 0 to ∼0.7 fit well with the Li(l) + Sn(l) + LiSn(l) + LiSn₂(l) + Li₂Sn(l) associate model. At X_Li > 0.7 no associate variations – including further associate variants such as Li₄Sn(l) etc. – could be fitted to the KEMS data. Nevertheless, in this work the Li(l) + Sn(l) + LiSn(l) + LiSn₂(l) + Li₂Sn(l) + Li₄Sn(l) + Li₉Sn(l) associate model was successfully fitted to the thermodynamic data of a selected literature study over the complete composition range. The thermodynamic data of the associate-forming reactions were also given in this paper