131 / 2022-03-14 00:19:39

Electronic Structure of a Cr-Doped [0001]/(1230)Σ7 Tilt Grain Boundary in ZnO

grain boundaries,varistors,DFT-calculations,zinc oxide

The safe operation of power equipment depends largely on the overvoltage protection level of surge arresters. ZnO varistors are widely used as the core components of surge arresters in power systems because of their excellent nonlinear V-I characteristics. It is important to study the electrical properties of ZnO varistors from the microstructure to guide the design and development of ZnO varistors. In this paper, the full relaxation of all atoms and the microscopic properties of [0001]/(1230)Σ7 symmetric tilt grain boundary containing Cr segregated atoms are studied using The first-principles calculations based on density functional theory. Chromium is one of the most important additives which contribute to the nonlinear V-I characteristics. The first-principles calculations were based on density functional theory (DFT) using the PBE GGA exchange-correlation functional. By investigating Cr doping in the bulk and [0001]/(1230)Σ7 symmetric tilt grain boundary in ZnO using ab-initio DFT-calculations, we obtain negative segregation energy suggesting that chromium accumulates in the grain boundary which is consistent with the experimental observations. The Cr segregation energy to the grain boundary was found to be large and negative indicating a significant driving force for the accumulation of Cr atoms in the grain boundary. Regarding the electronic structure, the electronic states in the vicinity of the bandgap are significantly affected by the Cr segregating at the grain boundaries. Deep electronic states are generated in the bandgap. Cr segregating at the grain boundaries play a central role in the nonlinear V-I characteristics.