Theoretical study of thermo-dynamical and thermoelectric properties of novel half-Heusler alloys AlNiAs and AlNiSb

Abstract

In the present report, the investigation related to the thermodynamical properties of both half-Heusler (HH) alloys ‘AlNiAs’ and ‘AlNiSb’ have been made under the framework of Density Functional Theory (DFT) by implementing quasi-harmonic approximations. The calculated value of Debye temperature for AlNiAs (ΘD = 344.890 K) is higher than that for AlNiSb (ΘD = 309.211 K). In addition to the thermodynamical properties, the thermoelectric properties are also explored by utilizing the semi-classical Boltzmann transport theory by combining it with DFT. The variation of thermoelectric parameters such as the Seebeck coefficient, electrical conductivity, power factor, and electronic thermal conductivity with chemical potential, temperature, and doping concentrations are investigated for the first time. Both HH alloys AlNiX (X = As and Sb) have a negative Seebeck coefficient, which indicates their n-type behavior. It is concluded from the present study that ‘AlNiSb’ is a more admirable thermoelectric material than ‘AlNiAs’ over the temperature range from 50 K to 800 K.