Multicomponent Silicides for Thermoelectric Materials by Jean-Claude Tedenac

Author:Jean-Claude Tedenac
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

In fact the relationship between chemical potentials of the phases and the system gives nonlinear equations that can be solved by numerical methods such as Newton-Raphson methods [60]. The CALPHAD-type packages use mathematical methods to minimize the Gibbs functions. It uses different data sources for the assessment of the systems going from classical thermal analysis to ab initio calculations.

Experimental data used for these calculations are those concerning the phase diagram measurements, enthalpy of formation of the compounds, enthalpy of mixing and EMF measurements , thermal analysis and X-ray diffraction. The results of ab initio calculations are also useful for using as input in the calculations, and they are taken into account with time. Those results are done at 0 K, but they can be extrapolated at 298 K, according to the fact that the temperature dependence in this temperature region is considered as negligible. The Gibbs energy of pure elements is taken with reference to the enthalpy of the elements in the SER state (standard element reference) and the elements in their stable state at 105 Pa and 298.15 K. This description is adopted from the SGTE database [65].

The purpose of this paper is not to describe in detail the method but to underline the applications. For a more precise knowledge of the problem, the reader can refer to the books which were presented in the first part of this chapter.

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