Thermodynamic analysis of the filling fraction limits for impurities in CoSb3 based on ab initio calculations

✍ Scribed by X. Shi; W. Zhang; L.D. Chen; J. Yang; C. Uher

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 321 KB
• Volume: 56
• Category: Article
• ISSN: 1359-6454
• DOI: 10.1016/j.actamat.2007.12.012

✦ Synopsis

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 4 Sb 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.