Enhanced Thermoelectric Properties in p‐Type Double Half‐Heusler Ti2−yHfyFeNiSb2−xSnx Compounds.

Double half‐Heusler Ti2FeNiSb2‐based compounds, which can be regarded as a combination of 17‐electron TiFeSb and 19‐electron TiNiSb, have a lower intrinsic thermal conductivity due to the smaller group velocity phonons and the disordered scattering by Fe/Ni. An enhanced room‐temperature Hall carrier concentration of ≈4.8 × 1021 cm−3 is achieved by doping Sn on the Sb site in a series of Ti2FeNiSb2−xSnx (x = 0.2, 0.3, 0.4, and 0.5) samples. Combined with the further decreased lattice thermal conductivity by alloying with Hf2FeNiSb2, a low lattice thermal conductivity of ≈1.95 W m−1 K−1 and a peak thermoelectric figure of merit (ZT) of ≈0.52 at 923 K are obtained in Ti1.6Hf0.4FeNiSb1.7Sn0.3, indicating the promising applications of double half‐Heusler compounds. [ABSTRACT FROM AUTHOR]