Understanding the origin of semiconducting ferromagnetic character along with the high figure of merit in Cs2NaMCl6 (M = Cr, Fe) double perovskites

Abstract

Thermoelectric devices have tendency to generate electric power by renovating waste heat. Semiconducting materials are the hunt for thermoelectric technology. We have traced the structural and mechanical stabilities, explored the electronic profile and thereafter unearthed the transport character of Cs2NaMCl6 (M = Cr, Fe) double perovskites. The electronic band structures and density of states from GGA and GGA + mBJ convey the semiconducting nature in both spin channels for these materials. The origin of semiconducting nature is explained with the help of crystal field splitting of d-orbitals. The optimization and asymmetric DOS across reference level suggest the ferromagnetic nature of double perovskites. The Boltztrap code with fixed relaxation time is used to determine the transport properties of Cs2NaMCl6 (M = Cr, Fe) double perovskites. The decreasing characteristic of Seebeck coefficient and resistance as a function of temperature suggests semiconductor character in these materials. The low thermal conductivity boosts the efficiency of materials to recover waste heat. The room temperature figure of merit (zT) is 0.71 and 0.79 for Cr and Fe-based double perovskites and with temperature, it increases. Thereby making these double perovskites suitable for waste heat harvesting. The results obtained while carrying out the investigation are in cohesion with available results in literature.