Mechanical and thermoelectric properties of FeVSb-based half-Heusler alloys

•Vickers method is extremely accurate to calculate the hardness value of samples.•Electrical conductivity was improved due to optimizing the carrier concentration.•A reduction in thermal conductivity was achieved due to point defect scattering.•Significant enhancement in thermoelectric figure of merit (zT) was achieved.•The highest zT value at 725 K was achieved for FeV0.60Nb0.4Hf0.16Ti0.2Sb sample. Half Heusler FeVSb-based compounds are recently identified as promising thermoelectric materials for medium to high temperature range. In this research article, thermoelectric properties of half Heusler FeV1−x-y-zHfxTiyNbzSb and FeVSb samples were studied over a temperature range from 300 to 800 K. Transition heavy elements such as Hf, Ti and Nb were used as dopants to enhance the phonon scattering aiming at reducing the material’s thermal conductivity. The FeV0.24Nb0.4Hf0.16Ti0.2Sb compound showed the lowest lattice thermal conductivity (κl) with a value of (1.81 ± 0.1 Wm−1 K−1) at room temperature with a reduction of ~82% compared with that of FeVSb compound. A maximum power factor value of (9.8 ± 0.9) μW cm−1 K−2 at 800 K and figure of merit (zT) value of 0.44 were recorded at 725 K for FeV0.24Nb0.4Hf0.16Ti0.2Sb. Vickers hardness method was used to estimate the hardness of the concerned alloys by micro-hardness technique, subjected to various applied loads. All the concerned samples showed significant mechanical stability. A maximum hardness value of 19.15 ± 0.77 GPa at load of 0.98 N was obtained for the FeV0.24Nb0.4Hf0.16Ti0.2Sb compound.