Material properties of nonstoichiometric solids
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 .
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