Performance advancements in P-type TaFeSb-based thermoelectric materials through composition and composite optimizations

Abstract

Half-Heusler compounds exhibit significant potential in thermoelectric applications for power generation up to 1000 K, notwithstanding the substantial challenges posed by the cost of constituent elements and the imperative to augment the average thermoelectric figure-of-merit (zT_ave) for more practical applications. Overcoming these obstacles demands advancing high-performance p-type TaFeSb thermoelectric materials with diminished Ta content. This investigation systematically explores the quaternary-phase space encompassing Ta, Nb, V, and Ti to ascertain an optimal composition, namely Ta_0.42Nb_0.3V_0.15Ti_0.13FeSb. This composition is characterized by a remarkable reduction in Ta concentration and an enhancement in zT, peaking at 1.23 at 973 K. Moreover, the integration of a high-mobility secondary phase, InSb, fosters enhancements in both the Seebeck coefficient and electrical conductivity, resulting in a 23% augmentation in the average power factor in the optimized composite, Ta_0.42Nb_0.3V_0.15Ti_0.13FeSb-(InSb)_0.015. This optimized material achieves a peak zT of 1.43 at 973 K, and a record-setting zT_ave of 1 from 300 K to 973 K, marking a significant advancement among p-type half-Heusler materials. Additionally, a single-leg device demonstrates a peak efficiency of approximately 8% under a temperature difference of 823 K vs. 303 K. These findings underscore the substantial potential of the proposed material design and fabrication methodologies in fostering efficient and sustainable thermoelectric applications.