Nonstoichiometric Phases—Composition, Properties and Phase Transitions

  • David SedmidubskýEmail author
  • Pavel Holba
Part of the Hot Topics in Thermal Analysis and Calorimetry book series (HTTC, volume 11)


Nonstoichiometric phases constitute a large family of technologically important materials. Among them, the inorganic materials whose variable stoichiometry of some components originates from their exchange with surrounding atmosphere represent particular thermodynamic systems referred to a partly open system. The phase equilibria in these systems including the homogeneous crystallochemical reactions of the involved crystal defects can be effectively treated using the thermodynamic potential called hyper-free energy derived from the Gibbs free energy by Legendre transformation with respect to the amounts of free components. In this chapter, we focus on general thermodynamic description of systems with variable content of components shared with a dynamical atmosphere, their essential material quantities being influenced by variable stoichiometry, conditions for homogeneous crystallochemical equilibria as well as for phase transitions. The influence of variable stoichiometry on material properties such as isobaric thermal expansion, isothermal compressibility and in particular heat capacity is analyzed and divided into two parts: the direct effect on conventional isoplethal quantities due to deviation from stoichiometry, and so-called saturation contributions determining the difference in material properties measured under isoplethal and isodynamical conditions (constant activities of free components). In the last part, the construction of phase diagrams of partly open systems is demonstrated on several examples of oxide systems, and the relevant phase transitions are classified and discussed.


Stable Component Clapeyron Equation Isochoric Heat Capacity Dynamical Atmosphere Free Component 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



P. Holba acknowledges the support of Ministry of Education of the Czech Republic in the framework of CENTEM PLUS project (LO1402) operated under the “National Sustainability Programme I.”


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© Springer International Publishing Switzerland 2017

Authors and Affiliations

  1. 1.Department of Inorganic ChemistryUniversity of Chemistry and Technology PraguePraha 6Czech Republic
  2. 2.New Technologies Research CentreUniversity of West BohemiaPragueCzech Republic

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