Determination of the thermodynamic properties of (s, sln) from a solid-electrolyte galvanic cell in the temperature range 1163 to 1318 K

Raghavan, Srini; Iyengar, G. N. K.; Abraham, K. P.

doi:10.1016/0021-9614(85)90058-8

Cited by 27 publications

(18 citation statements)

References 8 publications

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“…We estimate the consolute temperature to lie between 1160 and 1170 K, and thus our results provide strong support for the experimental results of Wood, Hackler, and Dobson, 7 ruling out the formation of a complete solid solution at temperatures as low as 600 K, as suggested by the data of Raghavan, Iyengar, and Abraham. 6 Although our calculated ⌬H mix vs composition curve is symmetric, our calculated phase diagram possesses a marked asymmetry with MnO less soluble in MgO than MgO in MnO. The same type of asymmetry is also observed in the CaO/MgO system, with the smaller cation more soluble in CaO than the larger cation in MgO.…”

Section: ͑6͒supporting

confidence: 63%

Free energy of solid solutions and phase diagrams via quasiharmonic lattice dynamics

et al. 2001

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We show how a configurational lattice dynamics technique, in which the free energy of a number of configurations is determined directly by means of a fully dynamic structural minimization, can be used to calculate thermodynamic properties of solid solutions and phase diagrams. No assumptions are made as to the nature of the solution and both configurational and vibrational entropy contributions are determined directly. Only a small number of configurations are required. We illustrate the method using MnO/MgO, for which our results support the recent experiments of Wood, Hackler, and Dobson ͓Contrib. Mineral. Petrol. 115, 438 ͑1994͔͒ who, in contrast to previous workers, suggest the formation of a complete solid solution at temperatures only above 1100 K.Solid solutions, alloys, and grossly nonstoichiometric compounds present considerable challenges to the theoretician, as does the calculation of absolute free energy. Ceramic solid solutions in particular are often strongly nonideal and approaches such as the cluster variation method ͑CVM͒, 1 widely used for metallic alloys, often perform poorly. In addition, despite the importance of accurate thermodynamic data for oxide solid solutions in such areas as ceramic fabrication and design and mineralogy, accurate thermodynamic data are rare.We have recently developed a highly efficient method for the fully dynamic structure optimization of large unit cells 2 that uses lattice statics and quasiharmonic lattice dynamics ͑QLD͒. We calculate the full set of free-energy first derivatives analytically, and a full minimization of the free energy with respect to all structural variables for large unit cells is possible. The accurate calculation of the free energy via QLD is quick and computationally efficient and does not resort to lengthy thermodynamic integration. Here we show this can be used for the free energies of solid solutions ͑in-cluding ⌬H mix and ⌬S mix ͒ and phase diagrams. The method is readily extended to elevated T and high P; no a priori assumptions are made regarding the configurational entropy contribution and the vibrational contribution is also evaluated straightforwardly.We illustrate our approach using MnO/MgO, for which not only are there several sets of experimental enthalpy data 3,4 but also conflicting reports of the phase diagram. As shown in Ref. 5, the experiments of Raghavan, Iyengar, and Abraham 6 suggest a consolute temperature, T c , as low as 600 K, whereas the results of Wood, Hackler, and Dobson 7 are consistent with a much larger T c ͑Ϸ1100 K͒ and a markedly asymmetric phase diagram. The data of Ref. 6 are indeed surprising given the CaO/MgO phase diagram, in which there is a large two-phase region, and the mismatch in ionic radii between Mn 2ϩ and Mg 2ϩ , which is substantial although smaller than between Ca 2ϩ and Mg 2ϩ . A further aim of this paper is to attempt to resolve this issue.In principle the solid solution can assume any state, i.e., each atom can be at any position. However, the only states of practical importance away from t...

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Section: ͑6͒supporting

confidence: 63%

Free energy of solid solutions and phase diagrams via quasiharmonic lattice dynamics

et al. 2001

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“…In Figure calculated enthalpy of mixing is shown together with experimental and first principle data . In Figures and the MgO and MnO activities, respectively, in the MgO‐MnO system are shown together with experimental data . The experimental enthalpy of mixing agree well with the first principle results by .…”

Section: Resultsmentioning

confidence: 97%

“…Several authors have made thermochemical investigations concerning mixing in the cubic monoxide ([NaCl]‐Mg x Mn 1−x O y ). All these studies have performed activity measurements, with the exception of which measured the enthalpy of mixing.…”

Section: Experimental Reviewmentioning

confidence: 99%

Thermodynamics of the Mg‐Mn‐O system—modeling and heat capacity measurements

et al. 2017

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In this study, a thermodynamic description of the Mg-Mn-O system is presented.Phase diagram data, structural information, and thermochemical data are used in the assessment. All solution phases are modeled using the compound energy formalism. In addition, heat capacity measurement of the MgMn 2 O 4 and Mg 6 MnO 8 phases are reported. The thermodynamic description reproduces thermochemical, structural, and phase diagram data. K E Y W O R D SCalphad, heat capacity, metal-matrix composite, Mg

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“…Note that we used the classic method of determination of the thermodynamic properties of solid compounds [18].…”

Section: Gibbs Energy Calculation By Open-circuit Chronopotentiometrymentioning

confidence: 99%

Electrochemical reduction of Gd(III) and Nd(III) on reactive cathode material in molten fluoride media

et al. 2008

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The electrochemical reduction of two lanthanides (neodymium Nd and gadolinium Gd) was investigated in the 800-950°C temperature range on nickel and copper electrodes. These materials react with lanthanides (Ln) to form intermetallic compounds. The formation mechanism of the alloys was determined by coupling electrochemical techniques and Scanning Electron Microscopy (SEM) after electrolyses runs; this also allowed the identification of the binary compounds formed. In addition, from the electrochemical results, we calculated the Gibbs energies of Nd/Ni, Gd/Ni, Gd/Cu and Nd/Cu.

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Determination of the thermodynamic properties of (s, sln) from a solid-electrolyte galvanic cell in the temperature range 1163 to 1318 K

Cited by 27 publications

References 8 publications

Free energy of solid solutions and phase diagrams via quasiharmonic lattice dynamics

Free energy of solid solutions and phase diagrams via quasiharmonic lattice dynamics

Thermodynamics of the Mg‐Mn‐O system—modeling and heat capacity measurements

Electrochemical reduction of Gd(III) and Nd(III) on reactive cathode material in molten fluoride media

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