Formation of liquid phase and nanostructures in flash sintered ZnO

This study presents the effects of current density limit on flash sintering and the formation of nanostructures in undoped ZnO. The combination of high electric field and low current density (1 and 2 A/cm²) results in the formation of hot spots and fracture as well as ZnO nanostructures in the vicinity of the hot spots. Such phenomena were not observed in the case of higher current density limit of 3 A/cm². A detailed microscopy analysis revealed that the growth of nanostructures initiated from liquid phase regions at the grain boundaries and within the grains.