The influence mechanism of donor doping from alkaline earth element on the thermoelectric properties of ZnO semiconductor materials for electricity meter

The study mainly uses point defect engineering (Ca doping) to modify the oxide thermoelectric material ZnO, and all experiments use ball milling mixing and spark plasma sintering system (SPS) to prepare samples to study the improvement of the thermoelectric performance of ZnO thermoelectric material with Ca element as the doping source. The thermoelectric properties of Ca doped ZnO have been systematically studied through experimental and theoretical calculation methods. The introduction of Ca element into ZnO matrix can decrease length of the bond of Zn–O, significantly increase the density of states near the Fermi level for the hybridization effect between the impurity level of the Ca atoms (mainly the d- orbits) and the Zn atoms (mainly the d- and p- orbits) and O atoms (mainly the p- orbits), and increase the corresponding carrier concentration, and electrical conductivity. The power factor obtained the maximum value of ~ 9.05 μWcm⁻¹ K⁻². The thermal conductivity and lattice thermal conductivity decrease due to the enhancement of heterogeneous scattering and the decrease of Young's modulus. Finally, the maximum ZT value of the Ca doped ZnO sample was increased to ~ 0.35 at 873 K at doping concentration x = 0.016, which is approximately ~ 3.57 times as that of the pure ZnO. Our experimental research has laid a good foundation for promoting the application of ZnO materials in high-temperature thermoelectric devices.