Structure and Failure Mechanism of the Thermoelectric CoSb3/TiCoSb Interface

The brittle behavior and low strength of CoSb3/TiCoSb interface are serious issues concerning the engineering applications of CoSb3 based or CoSb3/TiCoSb segmented thermoelectric devices. To illustrate the failure mechanism of the CoSb3/TiCoSb interface, we apply density functional theory to investigate the interfacial behavior and examine the response during tensile deformations. We find that both CoSb3(100)/TiCoSb(111) and CoSb3(100)/TiCoSb(110) are energetically favorable interfacial structures. Failure of the CoSb3/TiCoSb interface occurs in CoSb3 since the structural stiffness of CoSb3 is much weaker than that of TiCoSb. This failure within CoSb3 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 of the CoSb3/TiCoSb interface is similar to that of bulk CoSb3, but the ideal tensile strength and failure strain of the CoSb3/TiCoSb interface are much lower than those of bulk CoSb3. This can be attributed to the weakened stiffness of the Co Sb framework because of structural rearrangement near the interfacial region.