Structural, mechanical, electronic, and thermoelectric properties of new semiconducting d0 quaternary Heusler compounds CaKNaZ (Z =Si, Ge, Sn). A density functional theory study

Abstract

Due to the increasing demand for energy, the development of new and good thermoelectric (TE) materials is vital. In this study, ab initio calculations, based on the density functional theory (DFT) using the self-consistent full-potential linearized augmented plane wave (FPLAPW) method were performed to explore the structural, mechanical, electronic, and thermoelectric properties of quaternary alloys CaKNaZ (Z = Si, Ge, Sn) with quaternary Heusler structure. Optimization calculations confirmed the most stable structure for CaKNaZ (Z = Si, Ge, Sn) compounds is Y1-type in the non-magnetic phase. All of the compounds have been shown to behave like semiconductors, with band gaps of 0.84(1.34), 0.44(1.33), and 0.68(1.15), for CaKNaSi, CaKNaGe, and CaKNaSn respectively, using GGA(GGA-mbj) methods. The theoretical study of thermoelectric properties for CaKNaZ (Z = Si, Ge, Sn) was carried out by Boltzmann theory as implemented in BoltzTraP code. We have obtained a high figure of merit at moderate temperatures, indicating that the alloys under study can be used for thermoelectric applications.