High temperature reliability evaluation of CoSb3/electrode thermoelectric joints

The CoSb3/electrode thermoelectric (TE) joints were fabricated with the insertion of Ti foil by spark plasma sintering (SPS). The interfacial microstructure evolution and reliability of joints were investigated during accelerated thermal aging. After thermal aging, a multi-layer structure, which was composed of intermetallic compounds (IMCs), was observed at the CoSb3/Ti interface. The growth kinetics of IMC layers was studied. The theoretic life of CoSb3/electrode joints was predicted using the growth rate of IMC layers. The shear strength of aged CoSb3/electrode joints was also tested and the results showed the joints had sufficient strength for keeping the reliability of TE device. Scanning electron microscopy (SEM) showed that, in the aged sample, all fracture occurred inside of the IMC layers, while the fracture occurred in the Ti layer or Ti/TiSb interface in the un-aged sample. The results of four-probe tests showed that the electrical contact of CoSb3/electrode joint was good.