High Performance ZnO Varistors Prepared from Nanocrystalline Precursors for Miniaturised Electronic Devices

Suresh Pillai, Dublin Institute of Technology
Declan E. McCormack, Dublin Institute of Technology
John Kelly, Dublin Institute of Technology
Ramesh Raghavendra, Waterford Institute of Technology


An industrially viable solution-based processing route using minimal amounts of solvents has been used to prepare bulk quantity nano-powders (average particle size 15 ± 3 nm) for the fabrication of ZnO varistors. The xerogels, calcined powders and sintered materials were fully characterized. The preparation of varistors from nanopowders has been optimized by studying the 20 effect of temperature on grain growth, densification and breakdown voltage. The varistors are prepared by sintering at 1050 °C for 2 hours, a temperature which is ignificantly lower than the currently used industrial process. Highly dense varistor discs were prepared from the sintered material produce devices, with a breakdown voltage 85 % higher than that of commercial varistors,making them suitable for use in miniaturised electronic circuitry. Improved performance of these 25 materials has been attributed to the small grain size and better dispersion of additives on ZnO grains.