Temperature effect on mechanical response of flash-sintered ZnO by in-situ compression tests

Abstract

ZnO has been widely used for various industrial applications. Compared to the extensive investigations on the functional properties of ZnO, the mechanical behavior of ZnO is less well understood. Here we investigated temperature-dependent deformation mechanisms of flash-sintered and conventionally sintered ZnO by in-situ microcompression test up to 600 °C. When tested at room temperature, prominent transgranular cracking occurred in the flash-sintered ZnO at a flow stress of 1.2 GPa, higher than that for the conventionally sintered ZnO (0.9 GPa). A high density of dislocations formed near grain boundaries and fracture surfaces led to the high strength and work-hardening capability in the flash-sintered ZnO. At 200 °C, the flow stress of the flash-sintered ZnO decreased to 0.7 GPa, and the fracture mode evolved to intergranular cracking. When compressed at 400 °C, severe deformation localized at the pillar top was dominated by grain boundary-mediated processes. At 600 °C, plastically deformed grains and intergranular cracks increased prominently, accompanied by a decrease in the density of geometrically necessary dislocation. This study shed lights on understanding the influence of the flash sintering process on the mechanical behaviors of ZnO.