Self-assembled arrays of ZnO nanoparticles and their application as varistor materialsElectronic supplementary information (ESI) available: XRD plots and FESEM images. See http://www.rsc.org/suppdata/jm/b4/b400927d/

摘要

Linear arrays of ZnO nanoparticles have been successfully prepared by a simple sol–gel condensation reactioninvolving chemical modifiers, followed by drying (80 uC) and calcination (500 uC). The calcined material (nanoarrayZnO) is composed of approximately spherical nanoparticles of average diameter 21 ¡ 3 nm, selfassembledto form arrays extending in length to 2–4 mm. The morphology of the ZnO is found to dependsensitively on the amounts of chemical modifiers present. In their absence the ZnO produced (nano-ZnO) is anunstructured agglomerate of nanoparticles. The mechanism for formation of these linear arrays has beeninvestigated by examining the intermediates formed at 80 uC and 250 uC using XRD and TEM and byfollowing the decomposition reactions using TGA and DSC. Varistors prepared from the nano-array ZnO bysintering (1050 uC) with appropriate mixtures of metal oxides showed a breakdown voltage of 786 ¡ 30 Vmm21, which is substantially higher than that of samples prepared under similar conditions from either micronsizedcommercial ZnO (507 ¡ 30 V mm21) or from nano-ZnO (683 ¡ 30 V mm21).