| Summary: | Half-Heuslers (HHs) are promising thermoelectric materials with great compositional flexibility. Here, we extend work on the p-type doping of TiCoSb using abundant elements. Ti<sub>0.7</sub>V<sub>0.3</sub>Co<sub>0.85</sub>Fe<sub>0.15</sub>Sb<sub>0.7</sub>Sn<sub>0.3</sub> samples with nominal 17.85 p-type electron count were investigated. Samples prepared using powder metallurgy have negative Seebeck values, <i>S</i> ≤ −120 µV K<sup>−1</sup>, while arc-melted compositions are compensated semiconductors with <i>S</i> = −45 to +30 µV K<sup>−1</sup>. The difference in thermoelectric response is caused by variations in the degree of segregation of V(Co<sub>0.6</sub>Fe<sub>0.4</sub>)<sub>2</sub>Sn full-Heusler and Sn phases, which selectively absorb V, Fe, and Sn. The segregated microstructure leads to reduced lattice thermal conductivities, <i>κ<sub>lat</sub></i> = 4.5−7 W m<sup>−1</sup> K<sup>−1</sup> near room temperature. The largest power factor, <i>S<sup>2</sup></i>/<i>ρ</i> = 0.4 mW m<sup>−1</sup> K<sup>−2</sup> and <i>ZT</i> = 0.06, is observed for the n-type samples at 800 K. This works extends knowledge regarding suitable p-type dopants for TiCoSb.
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