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Published April 12, 2016 | Supplemental Material
Journal Article Open

p-Type Co Interstitial Defects in Thermoelectric Skutterudite CoSb_3 Due to the Breakage of Sb_4-Rings


Skutterudite CoSb_3 based thermoelectric devices have high potential for engineering applications because both n- and p-type doped CoSb_3 demonstrate excellent thermoelectric performance. A crucial point concerning the application of CoSb_3 is to understand and control its defect chemistry. To reveal the native conductivity behavior of nonstoichiometric CoSb_3, we investigated the intrinsic point defects in CoSb_3 using density functional theory. We found CoSb_3 is p-type in either Co or Sb rich regions of phase stability. Interstitial Co (Co_i) and interstitial Co-pair (Co_(i-p)) are the dominant point defects in the Co rich region. However, Co_(i-p) will be difficult to form because the formation temperature of Co_(i-p) is much lower than the synthesis temperature of CoSb_3. The unexpected acceptor nature of the Co_i or Co_(i-p) defects is explained by the breakage of multiple Sb_4-rings. Co vacancy (Co_v) is found to be the p-type defect in the Sb rich region. Furthermore, the solubility of excess Co in CoSb_3 is expected to be larger than that of Sb because of the lower formation energy and higher carrier concentration of Co_i compared with those of Co_v.

Additional Information

© 2016 American Chemical Society. Received: January 10, 2016. Revised: February 18, 2016. Published: March 22, 2016. This work is partially supported by National Basic Research Program of China (973-program) under Project No. 2013CB632505, the 111 Project of China under Project No. B07040, Materials Project by Department of Energy Basic Energy Sciences Program under Grant No. EDCBEE, DOE Contract DE-AC02-05CH11231, and China Postdoctoral Science Foundation (408-32200031). U.A. acknowledges the financial assistance of The Scientific and Technological Research Council of Turkey. H.X. and W.A.G. were supported by the National Science Foundation (DMR-1436985, program manager, John Schlueter). The authors declare no competing financial interest.

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