First-principles calculations to investigate Zr substitution enhanced thermoelectric performance of p-type ZrxHf1−xCoBi (x = 0,0.25,0.5,0.75,1) compounds

Abstract

Based on the first-principle calculation and semi-classical Boltzmann transport theory, the electronic structures and thermoelectric properties of Hf1−xZrxCoBi (x=0,0.25,0.5,0.75,1) compounds have been systematically investigated. These compounds possess narrow bandgaps and they are thermodynamically stable. The low frequency optical branches couple with the acoustic modes in the Zr doped compounds, which highly enhance the phonon scattering. The Zr substitutions hardly reduce the power factors when x=0.25 and 0.75, but substantially reduce the thermal conductivity and thus, improve the figure of merit. The predicted ZT of p-type Hf0.75Zr0.25CoBi and Hf0.25Zr0.75CoBi can reach up to 2.74 and 2.59 at 1200 K, which is much larger than that of the pure HfCoBi compound. This work implies that Hf0.75Zr0.25CoBi and Hf0.25Zr0.75CoBi are promising high-efficiency thermoelectric materials.