Synthesis and thermoelectric properties of n-type half-Heusler compound VCoSb with valence electron count of 19

Half-Heusler compounds with valence electron count (VEC) of 19 were not believed to have good thermoelectric properties because it was theoretically predicted as metallic. However, this work demonstrates experimentally that half-Heusler compound VCoSb we synthesized is in fact a good thermoelectric material. As-made samples show single half-Heusler phase and negative Seebeck coefficient with a peak value around −130 μV/K at 600 °C, which indicates the semiconductor-, not metallic-, like behavior. The VCoSb samples were made by arc-melting the elements to first form ingots, then ball-milling the ingots, and finally hot-pressing the fine powder to form the bulk materials. Different hot-pressing temperatures at 750 °C, 800 °C, and 900 °C were carried out and the results are discussed. A maximum thermoelectric figure-of-merit (ZT) around 0.5 is achieved at 700 °C for all the samples. - Highlights: • VCoSb samples were synthesized by arc-melting, ball-milling and hot-pressing. • VCoSb with 19 VEC shows semiconductor-like thermoelectric properties. • A peak power factor of 25 μW cm⁻¹ K⁻² is achieved at 700 °C. • ZT reaches 0.5 at 700 °C for all the samples hot-pressed at different temperature.