Brittle Failure Mechanism in Thermoelectric Skutterudite CoSb3

Guodong Li, Qi An, Wenjuan Li, William A. Goddard*, Pengcheng Zhai, Qingjie Zhang, G. Jeffrey Snyder

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

42 Scopus citations

Abstract

Skutterudites based on CoSb3 have high thermoelectric efficiency, but the low fracture strength is a serious consideration for commercial applications. To understand the origin of the brittleness in CoSb3, we examine the response along various shear and tensile deformations using density functional theory. We find that the Co-Sb bond dominates the ideal strength. Among all the shear and tensile deformation paths, shearing along the (001)/〉100〉 slip system has the lowest ideal strength, indicating it is the most likely slip system to be activated under pressure. We also find that, because the Sb-Sb covalent bond is softer than the Co-Sb bond, the Sb-rings are less rigid than the Co-Sb frameworks, which leads to the Sb-rings softening before the Co-Sb frameworks. Further deformation leads to deconstruction of Sb-rings and collapse of Co-Sb frameworks, resulting in structural failure. Moreover, we find that filling of the CoSb3 void spaces with such typical fillers as Na, Ba, or Yb has little effect on the ideal strength and failure mode, which can be understood because they have little effect on the Sb-rings.

Original languageEnglish (US)
Pages (from-to)6329-6336
Number of pages8
JournalChemistry of Materials
Volume27
Issue number18
DOIs
StatePublished - Sep 22 2015

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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