Electrical properties of Al2O3-doped ZnO varistors prepared by sol-gel process for device miniaturization

Al2O3-doped ZnO varistors with high performance have been fabricated with nano composite powders, which were prepared by the sol-gel method. The xerogels, calcined powders and sintered material ceramics were fully characterized. The electrical properties and grain boundary characteristics were measured. The average grain size decreased from 4.4 mu m to 3.0 mu m and the breakdown voltage increased from 720 V/cm to 1160 V/cm as the amount of Al2O3 increased from 0.0 wt.% to 0.40 wt.%. 2 ms square-wave test indicates that the energy capability was better in a sol-gel derived ZnO varistor than a conventional sample and was enhanced by Al2O3 doping. Improved electrical properties of sol-gel derived ZnO varistors is attributed to the smaller grain size and more uniform distribution of additives. Al2O3-doped ZnO varistor obtained from sol-gel process is useful for device miniaturization. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.