First-principle investigation on the thermoelectric and electronic properties of HfCoX (X=As, Sb, Bi) half-Heusler compounds

Abstract

In this work, we systematically calculated the thermoelectric and electronic properties of HfCoX (X ​= ​As, Sb, Bi) half-Heusler compounds. We found that for n-type HfCoAs and HfCoBi compounds at 1200 ​K, the dimensionless figure of merits can reach 1.74 and 1.49, respectively. These calculation results show that HfCoAs and HfCoBi compounds may have the potential to become the new high-temperature thermoelectric materials with excellent performance. HfCoX (X ​= ​As, Sb, Bi) compounds obey Born-Huang stability criteria and are dynamically and mechanically stable, brittle and anisotropic in mechanical properties. At 1200 ​K, due to the strong phonon-phonon interaction, the lattice thermal conductivities of HfCoAs and HfCoBi compounds are 8.08 ​W/mK and 4.97 ​W/mK, respectively. The lattice thermal conductivities of HfCoAs and HfCoSb compounds have similar values. The effective mass of HfCoAs conduction band is only 0.89 me, resulting in high relaxation time and carrier mobility.