A computational analysis of thermoelectric behaviour of d0 half-Heusler alloys GeKCa and GeKSr

The current study is based on the theoretical investigation of the thermoelectric properties of d(0) half-Heusler (HH) alloys GeKCa and GeKSr using Density Functional Theory (DFT). The calculations have been performed using the BoltzTrap code which is based on the semi-classical Boltzmann Transport theory incorporating the rigid band and constant relaxation time approximation. Different transport parameters such as Seebeck coefficient (S), electrical conductivity (sigma/tau), electronic thermal conductivity (kappa(e)/tau), power factor (S-2 sigma/tau) and figure of merit (zT) are evaluated and their variation with chemical potential (mu) is studied in a temperature range of 300-800 K with a gap of 100 K. The variation of these transport parameters have also been studied with respect to temperature. Lattice thermal conductivity of the compounds has also been calculated and found to be quite low at high temperatures. The observed transport properties indicate towards the alloys being p-type in nature. The highest value of S are observed to be 1948 mu V/K and 1512 mu V/K for GeKCa and GeKSr, respectively, at 300 K for p-type doping. Further, a high value of 0.63 and 0.60 is observed for the figure of merit, zT for GeKCa and GeKSr at 800 K, respectively. The observed thermoelectric properties suggest that both the HH alloys can be considered as good thermoelectric material for medium-temperature thermoelectric power generation applications.