Understanding sintering characteristics of ZnO nanoparticles by FIB-SEM three-dimensional analysis

In this study, we utilize three-dimensional (3D) reconstruction by focused ion beam (FIB) cutting and SEM imaging to understand the evolution of pore volume, pore-solid interfacial area, pore shape, pore connectivity, and pore number during the two-step sintering of ZnO nanoparticles. After the first-step sintering, the density is 75% and all the pores are connected. During the second-step sintering, the decrease of pore volume leads to the segmentation of pores and formation of closed pores. The shape of closed pores is irregular. The pore number first increases with the formation of closed pores, and then decreases due to the disappearance of small pores. The pore-solid interfacial area keeps decreasing during sintering. FIB-SEM 3D reconstruction offers an opportunity to directly and quantitatively observe the pore evolution and understand the sintering process at nanoscale.