Recent progress of half-Heusler for moderate temperature thermoelectric applications

Half-Heusler thermoelectric materials have been attracting extensive research interest over the last two decades. In this mini-review article, we summarize the synthesis methods for optimizing individual parameters to enhance the thermoelectric performance in both MNiSn (n-type) and MCoSb (p-type) based half-Heuslers. Some more recently available approaches, such as using metallic phase nanoinclus ions as dopants to enhance electrical conductivity and low energy carrier filtering to enhance Seebeck coefficient, resonant states near Fermi level for a higher Seebeck coefficient, and nanosized grains formed by rapid hot pressing to reduce thermal conductivity, are discussed in this article. In addition, the effect of high temperature annealing is also discussed, which is important for device performance.