Enhanced thermoelectric performance of polycrystalline InSb1−xBix by using isoelectronic substitution on the Sb site

Abstract

InSb has superior electronic transport with low bandgap and high mobility of charge carriers, however, its high lattice thermal conductivity makes it less applicable for thermoelectric applications. Herein we report an effective approach to simultaneously enhance the power factor and reduce total thermal conductivity by isoelectronic doping of Bi for Sb. A series of polycrystalline InSb 1-x Bi x is prepared. The enhanced power factor is attributed to the increase of carrier concentration by charge transfer from the Bi d -orbital states to the In 4 d -orbital states based on analyses of both the Bi and In L 3 -edge XANES spectra of InSb 1−x Bi x . The reduced total thermal conductivity arises from the reduced lattice thermal conductivity due to the point defects. The strain field fluctuations are evidenced by the blue shift in Raman spectra of InSb 1- x Bi x . As a result, zT = 0.56 is attained at 700 K, which is 16% higher than the pristine InSb. • Isoelectronic Bi doped InSb prepared by melting in an evacuated-and-encapsulated ampoule followed by hot pressing. • Isoelectronic doping of Bi on Sb sites leads to a reduced bandgap and effective enhancement of σ and σS 2 . • Increased carrier concentration due to charge transfer from the Bi d-orbital states to In 4 d -orbital states. • T -0.5 dependence of lattice thermal conductivity showing strong alloy scattering. • Blue shift in Raman spectra indicating compressive strain field fluctuations.