Brittle Failure Mechanism in Thermoelectric Skutterudite CoSb3

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• 作者：Guodong Li ; Qi An ; Wenjuan Li ; William A. Goddard ; III ; Pengcheng Zhai ; Qingjie Zhang ; G. Jeffrey Snyder
• 刊名：Chemistry of Materials
• 出版年：2015
• 出版时间：September 22, 2015
• 年：2015
• 卷：27
• 期：18
• 页码：6329-6336
• 全文大小：605K
• ISSN：1520-5002

文摘

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鈥揝b bond dominates the ideal strength. Among all the shear and tensile deformation paths, shearing along the (001)/鉄?00鉄?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鈥揝b covalent bond is softer than the Co鈥揝b bond, the Sb-rings are less rigid than the Co鈥揝b frameworks, which leads to the Sb-rings softening before the Co鈥揝b frameworks. Further deformation leads to deconstruction of Sb-rings and collapse of Co鈥揝b 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.