Material properties of nonstoichiometric solids
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Following our recently reported theoretical description of heat capacity of nonstoichiometric solids published in this journal, we extended this approach based on redefining the heat capacity conventionally valid for isoplethal conditions (fixed content of all components) to isodynamical conditions (controlled activity of a component shared with surroundings) and formulated a similar ansatz for other material characteristics such as thermal expansion and isothermal compressibility. As for the heat capacity, two additional terms are identified: the saturation contribution due to incorporation (or release) of the free component and the contribution due to deviation from stoichiometry. Involving some newly defined quantities reflecting the variation of stoichiometry with temperature, pressure, and activity, the resulting equations provide a direct link to experiment.
KeywordsNonstoichiometry Controlled atmosphere Heat capacity Thermal expansion Compressibility
This work has been accomplished within the CENTEM project, reg, No CZ.1.05/2.1.00/03.0088, which was funded from ERDF, operational programme VaVpI administrated by the Ministry of education of the Czech Republic. The idea to estimate the effect of nonstoichiometry on the dilatation contribution to heat capacity ensued from the discussion with prof. J. Leitner (ICT Prague) following the seminary lecture .
- 1.Hoitsema C. Palladium und Wasserstoff. Z Phys Chem. 1895;17:1–42.Google Scholar
- 2.Wald F. Elementare chemische Betrachtungen. Z Phys Chem. 1897;24:633–50.Google Scholar
- 3.Wald F. Was ist ein chemisches Individuum. Z Phys Chem. 1898;28:13–6.Google Scholar
- 4.Kurnakov NS, Glazunov AI. Zh Russ Chim Obshch. 1912;44:1007.Google Scholar
- 5.Kurnakov NS. Compound and chemical individuum. Bull Acad Imp Sci de St-Pétersbourhg. 1914;321–328 (in Russian); Verbindung und chemisches Individuum. Zeitschrift für anorganische Chemie. 1914;88;109–127.Google Scholar
- 6.Chaudron G. Reversible reactions of hydrogen and carbon monoxide on metallic oxides. Ann Chem. 1921;16:221–81.Google Scholar
- 9.Wagner C, Schottky W. Theorie der geordneten Mischphasen. Z Phys Chem B. 1930;11:163–210.Google Scholar
- 10.Brouwer G. A general asymmetric solution of reaction equations common in solid state chemistry. Philips Res Rep. 1954;9:366–76.Google Scholar
- 13.Maxwell JC. Theory of heat. London: Longmans, Green and Co; 1871.Google Scholar
- 14.Holba P. Thermodynamics of nonstoichiometric phases (in Czech). Proceedings of 35th Calorimetry Seminar, Třeboň, Czech Republic May 27th–31st, University of Pardubice, 2013, p. 109–112. ISBN 978-80-7395-611-0.Google Scholar
- 15.Gorski CA. Redox behavior of magnetite in the environment: moving towards a semiconductor model. PhD thesis, University of Iowa; 2009.Google Scholar