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 mu V/K at 600 degrees 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 degrees C, 800 degrees C, and 900 degrees C were carried out and the results are discussed. A maximum thermoelectric figure-of-merit (ZT) around 0.5 is achieved at 700 degrees C for all the samples. (C) 2015 Elsevier B.V. All rights reserved.