Enhanced Thermoelectric Performance of Bi-Based Half-Heusler Compounds XYBi (X: Ti, Zr, Hf; Y: Co, Rh, Ir)

Over the past few decades, Half-Heusler materials have garnered significant research attention for thermoelectric applications due to their cost-effectiveness, high thermal stability, mechanical strength, high power factor ( PF ), nontoxicity and moderate efficiency. Here, using first-principles density functional theory combined with the semiclassical Boltzmann transport equations, we systematically studied the thermoelectric properties of nine Bi-based Half-Heusler compounds, XY Bi (where, X =Ti, Zr, Hf; Y =Co, Rh, Ir). We demonstrate that these compounds exhibit a moderate band gap ( E g ) and an exceptionally high power factor ( PF ), outperforming many conventional thermoelectric materials. The high power factor primarily stems from the very high charge carrier concentration and high electrical conductivity. However, these Half-Heusler compounds show moderate thermal conductivity (κ). Based on our calculations, these Bi-based Half-Heusler compounds exhibit sufficiently high ZT values ranging from 0.56 to 1.98, with the highest values being 1.98 and 1.93 for n-type ZrRhBi and p-type HfRhBi, respectively. Our work reveals the inherent high ZT values in these previously less-explored Bi-based Half-Heusler compounds, indicating their strong potential for high-performance thermoelectric device applications.