Investigation of GaBi1-xSbx based highly mismatched alloys: Potential thermoelectric materials for renewable energy devices and applications

Abstract

The high-performance thermoelectric materials are considered a potential resource for clean and sustainable energy. Highly mismatched alloys (HMAs), that are admired for the dramatic modifications in their electronic band structures can essentially play important role in developing high-performance thermoelectric materials. Here, we explore the potential of GaBi1-xSbx based HMAs for their thermoelectric applications via density functional theory coupled with the Boltzmann transport theory. To perform a comprehensive analysis, four different Sb alloying compositions such as GaBi, GaBi0.875Sb0.125, GaBi0.75Sb0.25, and GaBi0.625Sb0.375, are considered. It is found that the Sb replacement over Bi in GaBi1-xSbx has stimulated two major modifications in the electronic band structure: the band-gap enhancement, and contraction in the curvature of conduction band minimum. These features have remarkably evolved the thermoelectric properties of GaBi1-xSbx as a function of Sb contents. The significant increase in Seebeck coefficient and decrease in the electrical conductivity of GaBi1-xSbx alloy as a function of Sb content have resulted in large values of thermoelectric power factor as well as the figure of merit (ZT). Considerable improvement in the ZT values as a function of Sb has been recorded that approaches to ~1.0 for GaBi0.625Sb0.375 at room temperature. The occurrence of optimal thermoelectric coefficient values, at attainable doping levels below the Fermi level reveals the predominantly p-type nature of the GaBi1-xSbx. Hence, GaBi1-xSbx (GaBi0.625Sb0.375 in particular) exhibits interesting thermoelectric properties at room temperature, and is therefore believed to be good candidate material for room temperature based thermoelectric devices and applications.