Electronic structure and thermoelectric properties of Pb-based half-Heusler compounds: ABPb (AÂ =Â Hf, Zr; BÂ =Â Ni, Pd)

The electronic structure and thermoelectric properties of half-Heusler ABPb (A = Hf, Zr; B = Ni, Pd) compounds were investigated by the first-principles calculation. Our results indicate all the four compounds are narrow-gap semiconductors. The value of power factor over relaxation time (S2σ/τ) first increases and then decreases with carrier concentration increasing, because of the narrower band gap. The optimal p- or n-type doping concentrations with different temperature have been estimated. Comparing with the experimental data of ZrNiPb, we get the thermopower S, power factor S2σ and the maximum power factor as a function of carrier concentration and temperature. Our calculated power factors are in good agreement with the experimental data, and give some suggestions to improve the thermoelectric properties.