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    Lattice evolution and point defect chemistry in Ta-doped ceria
    (2017-02-25)
    Charoonsuk, T.
    ;
    Vittayakorn, N.
    ;
    Kolodiazhnyi, T.
    Point defects in donor-doped ceria impact the physical, chemical and electronic properties. This work reports on the point defects in Ta-doped ceria, relating the changes in the lattice parameters with the type and concentration of point defects. The accurate Ce<sup>3+</sup> quantification using magnetization method is a key factor in solving the defect equilibria. Combining the experimental data and lattice expansion models it is demonstrated that the extra positive charge of Ta<sup>5+</sup> donors is compensated by both the Ce<sup>3+</sup> and the oxygen interstitials. An accurate quantitative analysis of the lattice expansion indicates that the theoretical calculations significantly overestimate the effect of the lattice response to oxygen interstitials. Furthermore, it is demonstrated that at high temperatures the anion Frenkel defects, whose concentration increases with the Ta substitution level, bring additional lattice expansion. The calculated enthalpy of formation of the anion Frenkel defects (H<inf>AF</inf> = 3.27–4.24 eV) for Ta-doped ceria is in good agreement with the ab-initio calculations and with the experimental values for the U-doped ceria. Furthermore, the accurate data of the lattice expansion caused by the interstitial oxygen reported here can be used to better understand and to predict the ‘swelling’ of the isomorphous UO<inf>2</inf>, PuO<inf>2</inf> and NpO<inf>2</inf> nuclear waste materials.
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    Thermodynamic models for determination of the solubility of 2,5-bis(2-furylmethylidene)cyclopentan-1-one in different solvents at temperatures ranging from 308.15 to 403.15K
    (2014-04-15)
    Prapasawat, Tatchanok
    ;
    Hronec, Milan
    ;
    Štolcová, Magdaléna
    ;
    Lothongkum, Anchaleeporn Waritswat
    ;
    Pancharoen, Ura
    The solubility data of 2,5-bis(2-furylmethylidene)cyclopentan-1-one (F<inf>2</inf>C) in solid-liquid equilibrium in alternative solvents are vital for a preliminary study of industrial applications aimed at producing sustainable and renewable materials and fuels. The solubility behavior of F<inf>2</inf>C in different solvents, such as tetrahydrofuran, mixed water-tetrahydrofuran (1:1, v/v), methanol, and water at temperatures ranging from 308.15 to 403.15K was investigated. An isothermal method was employed to measure the solubility data of F<inf>2</inf>C. The experimental data showed that the solubility of F<inf>2</inf>C increased as the temperature increased and was strongly affected by the surface tension and polarity index. The solubility of F<inf>2</inf>C in the studied solvents increased in the following order: H<inf>2</inf>O<methanol<H<inf>2</inf>O-THF mixture<THF. The thermodynamic models, such as the polynomial empirical equation, the Van't Hoff, and the modified Apelblat models were investigated to describe the experimental data. It was found that the modified Apelblat model was the most suitable for predicting the solubility behavior of F<inf>2</inf>C with a temperature increment. The calculated thermodynamic parameters indicated that in each studied solvent the dissolution process of F<inf>2</inf>C is endothermic and spontaneous. © 2014 Elsevier B.V.