Effect of Pressure on Thermoelectric Performance of Half Heusler Compounds

Abstract

In this work, the density functional theory (DFT) combined with Boltzmann transport equations are used to explore the effect of pressure on the structural, mechanical, thermal, and electronic properties of two half Heusler compounds PdXSn (X = Zr,Hf). The electronic band structure is tuned under pressure which enhances the thermoelectric properties of both compounds. The band gap opens with pressure and its value is 0.91 eV (1.26) for PdZrSn and 0.82 eV (1.16 eV) for PdHfSn at 0GPa (30GPa). The indirect nature does not alter at any pressure. The seebeck coefficient enhances from 900 μV/K to 1161 μV/K for PdZrSn and from 763 μV/K to 1012 μV/K for PdHfSn at pressure 0GPa to 30GPa. Similar trends observed in case of electrical conductivity and electronic part of thermal conductivity. But the lattice thermal conductivity is reduced from15.16 W/mKto 12.51 W/mK for PdZrSn and from 9.53 W/mK to 8.34 W/mK for PdHfSn at 30GPa respectively. Overall, the figure of merit ZT is elevated and attained maximum value of 0.45(0.55) for PdZrSn (PdHfSn) under pressure up to 30GPa.