TY - JOUR
T1 - Brittle Failure Mechanism in Thermoelectric Skutterudite CoSb3
AU - Li, Guodong
AU - An, Qi
AU - Li, Wenjuan
AU - Goddard, William A.
AU - Zhai, Pengcheng
AU - Zhang, Qingjie
AU - Snyder, G. Jeffrey
PY - 2015/9/22
Y1 - 2015/9/22
N2 - 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.
AB - 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.
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U2 - 10.1021/acs.chemmater.5b02268
DO - 10.1021/acs.chemmater.5b02268
M3 - Article
SN - 0897-4756
VL - 27
SP - 6329
EP - 6336
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 18
ER -