Nanostructure of ZnO fabricated via French process and its correlation to electrical properties of semiconducting varistors

The rich nanostructural diversity of commecial zinc oxide, fabricated via French process, is investigated. FESEM images of ZnO nanostructures reveal nanorods, nanoplates, nanoboxes, nanomallets, microclusters, polyhedral drums and irregularly-shaped particles (ISPs). Due to nanoscopic inhomogeneity in crystallisation conditions, many types of ZnO nanostructures coexist (and codiffuse) even in a minute region of 1 μm3. The nanostructures generally grow in either the [0001] or the [1010] plane directions. EDS analysis reveals that hexagonal-like nanorods/drums possess higher oxygen-to-zinc atomic ratios than that of the rectangular-like nanoplates/boxes. A correlation between ZnO nanostructure and semiconducting varistors shows that nanorod-rich specimens exhibit superior nonlinearity but poorer energy handling.