Advancing the reliability of thermoelectric materials: A case study of silicides through statistics

This work presents a statistical study of mechanical properties of a pair of silicide thermoelectric (TE) materials, p-type higher manganese silicide (HMS), and bismuth-doped n-type magnesium silicide stannide. The fracture strength of each material was examined with a statistically significant number of samples to obtain useful information for subsequent engineering work. Furthermore, to lend credibility to our measurements, we applied an ASTM standard (ASTM C1161) toward the determination of the mechanical properties instead of using nonstandard approaches. This approach, rarely undertaken for TE materials, was enabled by following large-scale synthetic capabilities that met the size requirements of this standard without compromising the thermoelectric figure-of-merit. The distributions of fracture strengths of the pair of silicide materials were established, and the fracture mechanisms elucidated through analyses of the fractured surfaces. Using this information, we were able to improve the fracture strength of p-type HMS through a minor addition of vanadium without compromising the figure-of-merit ZT. Together, these results advance the reliability of silicide TE materials, making them attractive candidates for large-scale deployment.