First principles calculations to investigate Li-based quaternary Heusler compounds LiHfCoX (X = Ge, Sn) for thermoelectric applications

Abstract

In the last few decades, varieties of semiconductors have been explored for electronic and thermoelectric applications. As a result of these motivations, the current research work investigates the structural, electronic, vibrational, elastic, mechanical, thermodynamic, and thermoelectric properties of two quaternary Heuslers (QHs), namely LiHfCoGe and LiHfCoSn (both of which are semiconducting in nature), within the computational framework of DensityFunctional Theory (DFT) and Boltzmann transport equations. Both alloys display the p-type semiconductivity, dynamical stability and crystallize in the FCC cubic structure within F-43 m space group. The high Seebeck coefficient values pronounce an excellent and fundamental thermoelectric character. The large melting points expose their scope in the high-temperature regions. However, all of the thermoelectric characteristics are also measured in terms of the estimated relaxation time using deformation potential theory. Even though the figure of merit (ZT) is in the middle of the pack yet better than many compounds of the same sort. The impact of spin–orbit coupling on the thermoelectric characteristics is also examined. The practical utilization of the materials can be evaluated from the elastic and mechanical properties that are favorable in manufacturing efficient and reliable Thermoelectric Modules at high-temperatures.