Improvement mechanism of thermoelectric properties of ZnO ceramics by energy band regulation

Abstract

ZnO based thermoelectric material is one of the most promising thermoelectric materials in the high temperature zone at present. Since its thermoelectric performances are closely related to the electronic band structure, energy band regulation was adopted through doping and composition optimization in order to improve its thermoelectric conversion efficiency. By introducing tetravalent Si elements at Zn sites of the ZnO matrix, the bandgap has been effectively reduced and the synergistic optimization of various thermoelectric parameters is achieved. The hybridization of the s - and p - orbitals of Zn atoms, the p - orbitals of O atoms, and the p - orbitals of Si atoms were introduced, and correspondingly increase the density of states near the Fermi level, increase the carrier concentration and electrical conductivity, and reduce the Seebeck coefficient. Due to the scattering of heteroatoms, the thermal conductivity decreases. Combined with the increase in power factor and the decrease in thermal conductivity, the ZT values obtained an effective improvement, reaching a maximum of ∼0.408 at 873 K, which is as ∼4.12 times that of the ZnO sample. The method exhibits simple process, and is conducive to batch production and low-cost preparation of high-performance thermoelectric materials, which is of great significance for expanding the application fields of ZnO based thermoelectric materials.