Transport and thermoelectric properties of Nb-doped FeV0.64Hf0.16Ti0.2Sb half-Heusler alloys synthesized by two ball milling regimes

•P-type FeV0.64−xNbxHf0.16Ti0.2Sb alloys are prepared by arc melting followed by induction melting.•The samples were milled in two milling regimes and then sintered with spark plasma.•Thermoelectric properties were studied as functions of temperature from 300 K to 800 K.•The weighted mobility, µw, and electronic quality factor, BE, were calculated.•The maximum zT value at 725 K was achieved for BM-ed FeV0.60Nb0.4Hf0.16Ti0.2Sb sample.