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Thermodynamic analysis of the filling fraction limits for impurities in CoSb3based on ab initio calculations

Authors
Journal
Acta Materialia
1359-6454
Publisher
Elsevier
Publication Date
Volume
56
Issue
8
Identifiers
DOI: 10.1016/j.actamat.2007.12.012
Keywords
  • Thermoelectric
  • Ab Initio Calculations
  • Cosb3
Disciplines
  • Chemistry
  • Physics

Abstract

Abstract The thermodynamic stabilities of alkaline earth (Ca, Sr and Ba), and rare earth (La, Ce and Yb), filled CoSb 3 skutterudites have been studied using a plane-wave density functional method. By combining the formation energy of inserting an impurity into the intrinsic void of CoSb 3 and that of secondary phases ISb 2 and CoSb 2, it is found that the filling fraction limit (FFL) or the maximum filling fraction of an impurity I corresponds to the minimum formation energy for a mixed chemical reaction route that results in the formation of filled skutterudite I y Co 4Sb 12 at the maximum filling as well as the formation of secondary phases. Theoretically estimated FFLs of various impurities in the voids of CoSb 3 are in good agreement with the reported experimental data. A schematic phase diagram for filled CoSb 3 is given. Discussion on the effect of the ionic radius of a filler and the content of Sb on FFL is presented.

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