Structure and Failure Mechanism of the Thermoelectric CoSb_3/TiCoSb Interface

The brittle behavior and low strength of CoSb_3/TiCoSb interface are serious issues concerning the engineering applications of CoSb_3 based or CoSb_3/TiCoSb segmented thermoelectric devices. To illustrate the failure mechanism of the CoSb_3/TiCoSb interface, we apply density functional theory to investigate the interfacial behavior and examine the response during tensile deformations. We find that both CoSb_3(100)/TiCoSb(111) and CoSb_3(100)/TiCoSb(110) are energetically favorable interfacial structures. Failure of the CoSb_3/TiCoSb interface occurs in CoSb_3 since the structural stiffness of CoSb_3 is much weaker than that of TiCoSb. This failure within CoSb_3 can be explained through the softening of the Sb–Sb bond along with the cleavage of the Co–Sb bond in the interface. The failure mechanism the CoSb_3/TiCoSb interface is similar to that of bulk CoSb_3, but the ideal tensile strength and failure strain of the CoSb_3/TiCoSb interface are much lower than those of bulk CoSb_3. This can be attributed to the weakened stiffness of the Co–Sb framework due to structural rearrangement near the interfacial region.