Interfacial evolution behavior and reliability evaluation of CoSb3/Ti/Mo-Cu thermoelectric joints during accelerated thermal aging

Interfacial structure plays a critical role for the reliability of thermoelectric (TE) device. This study investigated the interfacial evolution behavior and the reliability of CoSb3/Ti/Mo-Cu TE joints during accelerated thermal aging. After thermal aging, three-layer intermetallic compound (IMC) structure was observed at the CoSb3/Ti interface, and EDS analysis confirmed that the IMC layers were composed of TiCoSb, TiSb2 and TiSb. The total thickness of IMC layers increased linearly with the square root of aging time. The growth kinetics of IMC layers was studied. The theoretic life of CoSb3/Ti/Mo-Cu TE device was predicted using the growth rate of IMC layers. The shear strength of aged CoSb3/Ti/Mo-Cu TE joints was also investigated and the results showed the joints had sufficient strength after aging at 575 °C for 720 h. SEM showed that, in all the aged samples, the fracture occurred inside of the IMC layers, while the fracture occurred in the Ti layer or Ti/TiSb interface in the un-aged samples.