Influence of ohmic grain boundaries in ZnO varistors
- Solid State Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6030 (United States)
- Hubbell Incorporated, The Ohio Brass Company, 8711 Wadsworth Road, Wadsworth, Ohio 44281 (United States)
A realistic model of transport properties of zinc oxide varistors is constructed from two-dimensional Voronoi networks and studied via computer simulations. In agreement with experimental microcontact measurements made on individual junctions, the networks are assumed to contain randomly distributed microjunctions of two types: (1) electrically active with highly nonlinear current-voltage ({ital I}-{ital V}) characteristics and (2) ohmic, i.e., with linear {ital I}-{ital V} characteristics. Effects of the ohmic grain boundaries in the network are simulated for various concentrations and resistivities. Shapes of the simulated {ital I}-{ital V} characteristics and current dependence of the coefficient of nonlinearity of the network are in good agreement with those experimentally observed for thin varistor samples and in the measurements employing various surface electrode patterns. It is found that the breakdown voltage of the networks increases with the number of the ohmic grain boundaries, except when their resistivity is so low that it becomes comparable with that of the ZnO grains. The maximal value of the coefficient of nonlinearity of the network is shown to be insensitive to the presence of the ohmic grain boundaries, regardless of their resistivity and concentration. {copyright} {ital 1996 American Institute of Physics.}
- Research Organization:
- Oak Ridge National Laboratory
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 256756
- Journal Information:
- Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 1 Vol. 79; ISSN JAPIAU; ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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