Varistors based on nanocrystalline powders produced by mechanical grinding
US6620346B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 28, 2000 |
| Grant date | Sep 16, 2003 |
| Priority date | — |
| Expiry date | Apr 28, 2020 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01C7/112
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
The invention concerns novel varistors based on zinc oxide and a method for making same, which consists in using as base products nanocrystalline powders obtained by high-intensity mechanical grinding and in subjecting the mixture resulting from said nanocrystalline powders a consolidating treatment such as sintering, in suitably selected temperature and time conditions so as to retain the smallest possible grain size of ZnO. The resulting varistors have a very fine homogeneous microstructure and an average grain size characteristically not more than 3 mu m, i.e. five times smaller than standard materials. Said novel varistors have a larger number of grain boundaries per length unit and therefore a much higher breakdown voltage. Said voltage is characteristically higher than 10 kV/cm and can reach 17 kV/cm which is almost one order of magnitude above the breakdown voltage of standard varistors. The non-linearity coefficient of the current-voltage curve is also improved, and is greater than 20 and can reach values as high as 60. Moreover, the leakage currents below the breakdown voltage of said varistors, are much weaker.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.