Improving the voltage holdoff performance of alumina insulators in vacuum through quasimetallizing
Treatment of the surface of an alumina insulator with coatings incorporating varying amounts of Cr, Mn, and Ti can significantly increase the vacuum voltage holdoff capability of the insulator (up to 25%). During processing (quasimetallizing) the coating penetrates into the alumina, so it is insensitive to mechanical damage. This quasimetallizing treatment is also compatible with subsequent metallizing and brazing of the alumina insulator. A 7 Mn:1 Ti mix performed very well, being found to be as effective on a 94% Al/sub 2/O/sub 3/ alumina as on the previously investigated 95% Al/sub 2/O/sub 3/, 1% Cr/sub 2/O/sub 3/ alumina. Mixes of 6 Mn:1 Ti:1 Ca and 6 Mn:3 Cr performed about as well as the 7 Mn:1 Ti mix, but no better. Quasimetallizing with pure Mn improved the voltage holdoff capability of alumina by about half as much as when using the 7 Mn:1 Ti mix. Mixes with relatively high titanium content (4 Mn:3 Ti and 3 Mn:3 Ti:2 Cr) significantly increased the voltage holdoff capability of the alumina, but unfortunately were much more prone than the 7 Mn:1 Ti mix (or plain alumina) to suffer severe and permanent damage when a breakdown did occur. Quasimetallizing with appropriate formulations has been shown to change the surface characteristics of alumina in two ways: it decreases the surface resistivity of the alumina, and it decreases the secondary electron emission yield of the alumina. Each change improves the voltage holdoff characteristics of the alumina.
- Research Organization:
- General Electric Co., St. Petersburg, FL (USA). Neutron Devices Dept.
- DOE Contract Number:
- EY-76-C-04-0656
- OSTI ID:
- 6138363
- Report Number(s):
- GEPP-TIS-441; TRN: 79-017015
- Country of Publication:
- United States
- Language:
- English
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Improving the voltage holdoff performance of alumina insulators in vacuum by quasimetallizing or doping
Improving the voltage holdoff performance of alumina insulators in vacuum by quasimetallizing or doping
Related Subjects
ALUMINIUM OXIDES
PERFORMANCE
CHROMIUM
SURFACE COATING
ELECTRICAL INSULATORS
MANGANESE
TITANIUM
BRAZING
ELECTRIC CONDUCTIVITY
SURFACE PROPERTIES
TESTING
ALUMINIUM COMPOUNDS
CHALCOGENIDES
DEPOSITION
ELECTRICAL EQUIPMENT
ELECTRICAL PROPERTIES
ELEMENTS
EQUIPMENT
FABRICATION
JOINING
METALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
TRANSITION ELEMENTS
WELDING
360201* - Ceramics
Cermets
& Refractories- Preparation & Fabrication
360204 - Ceramics
Cermets
& Refractories- Physical Properties