Crystal structure, chemical bond and enhanced performance of β- Zn4Sb3 compounds with interstitial indium dopant

In-doped b-Zn4Sb3 compounds (Zn-4 xInxSb3, 0 less than or similar to x greater than or similar to 0.24) were prepared by melt-quenching and spark plasma sintering technology in the work. The resultant samples were systematically investigated by X-ray diffraction, X-ray photoelectron spectroscopy, differential scanning calorimetry and thermoelectric property measurements. The In dopant was identified to preferentially occupy the interstitial site in beta-Zn4Sb3 and led to the local structural perturbations near the 12c Sb2 and 36f Zn1 sites. The Auger parameters of Zn and Sb indicated that the increase in the valence of Zn was attributed to the charge transfer from Zn to In atoms. The binding energies of In 3d5/ 2 core level showed that the interstitial In dopant was n-type dopant (In3+) in slightly In-doped Zn-4 xInxSb3, but acted as acceptor and was p-type dopant (In+) in heavily In- doped ones. The discovery provides a reasonable explanation for the puzzled relation between r and x for Zn-4 xInxSb3. Simultaneously increasing the electrical conductivity and Seebeck coefficient of Zn-4 xInxSb3 can be realized through the local structural perturbations. The significantly enhanced power factor and the intrinsic low thermal conductivity resulted in a remarkable increase in the dimensionless figure of merit (ZT). The highest ZT reached 1.41 at 700 K for Zn3.82In0.18Sb3 and increased by 68% compared with that of the undoped beta-Zn4Sb3.