3.3. Contact resistivity of Mo–Ti/Yb–SKD interface
Fig. 9. Electrical resistivity of the Ni/Mo–Cu/Mo5Ti95/Yb–SKD thermoelectric joints aged at 550 °C for various days.Figure optionsDownload full-size imageDownload as PowerPoint slide
Fig. 10. Evolution of contact resistivity vs aging time for Mo–Ti/Yb–SKD joints at 550 °C.Figure optionsDownload full-size imageDownload as PowerPoint slide
Fig. 11. Cracks in material of Mo15Ti85/Yb–SKD joints aged at 550 °C for 12 days.Figure optionsDownload full-size imageDownload as PowerPoint slide
In this G-1 study, a suitable structure consisting of a Mo–Cu buffer layer and a Mo–Ti barrier layer was introduced into Ni/Yb–SKD joints. The 300 μm Mo55Cu45 buffer layer exhibited a good thermal shock resistance, which solved the CTE mismatch between the Ni electrode and Yb–SKD material. Mo–Ti alloy replaced traditional Ti as a barrier layer. After aging at 550 °C, the diffusion layers changed from TiCoSb, TiSb2 and TiSb in the Ti/Yb–SKD system to TiCoSb, Ti3Sb2 and Ti2Sb in the Mo–Ti/Yb–SKD system. A small amount of Mo in Ti hindered the diffusion of Ti effectively and reduced the contact resistivity at the same time. However, excess Mo led to more of a CTE mismatch. Considering the above two aspects, Mo5Ti95 appeared to be an appropriate barrier layer. Thus a reliable Yb–SKD/Mo–Ti/Mo–Cu/Ni TE joint was fabricated successfully.