Interfacial structure and stability in Ni/SKD/Ti/Ni skutterudite thermoelements

Ni/Ti/SKD/Ni (SKD: skutterudite) thermoelements were fabricated by spark plasma sintering and electroplating procedures. The interfacial stability was evaluated by long-term isothermal aging and multi-round thermal shock tests. The interfacial diffusion at Ni/SKD and Ni/Ti in the thermoelements during high temperature aging up to 15days was systematically studied by scanning electron microscopy with elemental distribution. The growth kinetics of the intermetallic compounds was analyzed, and the coefficients of the intermetallic compound growth rate were calculated. For the Ni/SKD interface, there was no inter-diffusion at temperatures below 200°C. However, three intermetallic compound layers for the Ti/Ni interface were confirmed to be TiNi3, TiNi and Ti2Ni sequentially from the Ni side to the Ti side at temperatures above 500°C, leading to an interfacial structure of Ti/Ti2Ni/TiNi/TiNi3/Ni. All interfaces maintained good bonding strength after long-term isothermal aging and multi-round thermal shock tests. The experimental data demonstrated that Ni is an ideal candidate as the electrode of skutterudite thermoelements at both the hot and cold sides. •We developed Ni material as the electrode for skutterudite thermoelement.•The Ni electrode had a good adhesion with the Ti barrier layer and skutterudites.•For Ni/Skutterudite interface there was no inter-diffusion below 200°C.•For Ti/Ni interface there were three intermetallic compounds above 500°C.•The Ti/Ni and Ni/SKD interfaces showed satisfied stability after aging and thermal shock.