Development of Indium-Tin Oxide Diffusion Barrier for Attaining High Reliability of Skutterudite Modules

Thermoelectric (TE) modules that operate at an intermediate-temperature range (600-900 K) inevitably face reliability issues during their operation when subjected to prolonged thermal cycling or due to the aging of the materials. To maintain the sustained performance of TE modules, antiaging techniques such as antioxidation coating and vacuum packaging are necessary. Metallization is one of the key technologies for fabricating highly reliable TE modules because the resulting metal layer can serve as a diffusion barrier preventing an elemental diffusion. Herein, indium-tin oxide (ITO) was investigated as a diffusion barrier for skutterudite (SKD); the compound has high conductivity compared to other oxides and low reactivity compared to metals. Ti/ITO/SKD-structured TE legs were fabricated by co-sintering using a spark plasma sintering system. The ITO layer was found to considerably suppress elemental diffusion by forming Ti-O bonding at the interface. The electrical contact resistance was also maintained at a low level both before and after the thermal aging. An eight-couple TE module was used to verify the reliability of the as-synthesized SKD module. The maximum power density of the Ti/ITO/SKD module was found to be approximately 1 W/cm². A thermal cycling test, run for 500 cycles, was conducted for both Ti/SKD and Ti/ITO/SKD structures. It confirmed that the power output of the Ti/ITO/SKD-structured module is maintained, while the power output of the Ti/SKD-structured module decreased 1% after the thermal cycling. In conclusion, the as-developed TE module, owing to its high durability and reliability, was successfully fabricated.