Exploring the suitability of narrow-bandgap compounds for thermoelectric application

Abstract

Abstract Different opinion exists regarding the role of bandgap size on thermoelectric variables. Motivated by the observation that the band shape can in a definite way affect thermoelectric properties, two compounds (BaSiSr and IrBiZr) have been evaluated for optimum thermoelectric application. The phonon spectrum, band structure, mechanical and thermoelectric properties of the two compounds were investigated using the density functional theory. The calculated bandgap size of the compounds are comparable (IrBiZr = 0.223 eV; BaSiSr = 0.220 eV). The valence energy edge peaked at the Fermi level for both compounds. The highest valence energy edge occurred at a single high symmetry point (Γ for IrBiZr) but at two symmetry points (X and W for BaSiSr). IrBiZr gave an overall superior performance over BaSiSr in the calculated elastic, thermodynamic and thermoelectric parameters. A lesser role for bandgap size can therefore be indicated in the design and optimization of novel thermoelectric materials in view of better results in favor of IrBiZr than BaSiSr.