Ni substitution enhanced thermoelectric properties of ZrPd1−xNixPb (x = 0,0.25,0.5,0.75,1)

Based on the first-principles calculations, we systematically studied the electronic structure and thermoelectric properties of ZrPd1−xNixPb (x = 0, 0.25, 0.5, 0.75, 1) compounds with the mBJ potential and mBJ + SOC method. By using the calculated band structures and Boltzmann transport theory, we studied the thermopower S, power factor over relaxation time S2σ/τ, and optimal carrier concentration for both of p- and n-type compounds. Our results indicate that all the compounds are thermodynamically stable narrow-gap semiconductors, with the band gaps ranging from 0.094 to 0.435 eV. The x = 0.25 and 0.75 compounds are direct band gap semiconductors, while the pure ones are indirect band gap semiconductors. The optimal carrier concentration and corresponding power factor (S2σ/τ) for x = 0, 0.25, 0.75, and 1 compounds are very close in p-type. The Ni substitution significantly decreases the lattice thermal conductivity from 26.4 Wm−1K−1 (x = 1) to 6.37 Wm−1K−1 (x = 0.25) at 300 K, without reducing the S2σ/τ. The lower lattice thermal conductivities of ZrPd0.25Ni0.75Pb and ZrPd0.75Ni0.25Pb suggest good thermoelectric properties. The cost of the alloy can also be decreased by the Ni substitution, whose price is only about 0.2% of the Pd metal.