Double half‐Heuslers comprising two aliovalent half‐Heuslers are promising candidates for thermoelectric materials because of their intrinsically low lattice thermal conductivity; however, poor electronic transport properties need to be overcome. Herein, the effects of Sn doping on the electronic and thermal transport properties of p‐type Ti2FeNiSb2 to enhance the thermoelectric performance via the compositional tuning route are investigated. The power factor is significantly improved owing to the synergetic effect of the increase in the density‐of‐states effective mass and the carrier concentration. In addition, the lattice thermal conductivity is slightly reduced, benefitted from intensified phonon scattering due to lattice disordering by Sn substitution at the Sb‐site. A peak figure of merit (zT) of ≈0.28 is obtained at 973 K in Ti2FeNiSb1.8Sn0.2, which is almost twice higher than that of the pristine Ti2FeNiSb2.

Compositional tuning is one of the important approaches to enhance the electronic and thermal transport properties of thermoelectric materials since it can generate point defects as well as control the phase evolution behavior. Herein, we investigated the Ti addition effect on the grain growth during melt spinning and thermoelectric transport properties of Hf0.5Zr0.5NiSn0.98Sb0.02 half-Heusler compound. The characteristic grain size of melt-spun ribbons was reduced by Ti addition, and very low lattice thermal conductivity lower than 0.27 W m−1 K−1 was obtained within the whole measured temperature range (300–800 K) due to the intensified point defect (substituted Ti) and grain boundary (reduced grain size) phonon scattering. Due to this synergetic effect on the thermal transport properties, a maximum thermoelectric figure of merit, zT, of 0.47 was obtained at 800 K in (Hf0.5Zr0.5)0.8Ti0.2NiSn0.98Sb0.02.

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