Claims
- 1. A high voltage holdoff metal-to-ceramic seal for a vacuum device, said seal comprising:
- a metallic conductor;
- a body of ceramic material in sealing contact with said metallic conductor; and
- a region of cermet material substantially integral with said ceramic material and in electrical contact with said conductor, said cermet material having a resistivity less than said ceramic material, whereby the resultant resistivity gradient in said seal is effective to substantially increase the voltage holdoff capacity of said seal.
- 2. A metal-to-ceramic seal of claim 1, wherein said cermet material and said ceramic material have about the same coefficient of expansion.
- 3. A metal-to-ceramic seal of claim 2, wherein said ceramic material comprises aluminum oxide and said cermet material comprises a mixture of aluminum oxide and metallic material.
- 4. A metal-to-ceramic seal of claim 2, wherein said ceramic material comprises aluminum oxide and said cermet material comprises a mixture of aluminum oxide and molybdenum.
- 5. A metal-to-ceramic seal of claim 1, wherein said cermet material has a resistivity about 20 orders of magnitude less than the resistivity of said ceramic material.
- 6. A metal-to-ceramic seal of claim 1, wherein said ceramic material is essentially tubular and said region of cermet material is essentially annular.
- 7. A metal-to-ceramic seal of claim 6 wherein said cermet material is contained within a recess in an end surface of said ceramic material in contact with said metallic conductor.
- 8. A metal-to-ceramic seal of claim 7 wherein the recess has a rectangular cross-section and the depth of the recess is greater than the width of the recess.
- 9. A ceramic-to-metal seal of claim 8 wherein the width of the recess is about 1/4 the width of said ceramic surface.
- 10. A high voltage holdoff seal for a vacuum device, said seal comprising:
- a low resistivity metallic conductor;
- a body of high resistivity ceramic material having a surface in vacuum sealing contact with said metallic conductor; and
- means, extending from said surface into said body, for reducing the resistivity of said body near said surface to substantially increase the voltage holdoff capacity of said seal.
- 11. A high voltage holdoff seal of claim 10 wherein said means comprises a cermet material extending into a recess in said body.
Government Interests
The U.S. Government has rights in this invention pursuant to contract No. DE-ACO4-76DP00656 between the U.S. Department of Energy and General Electric Co.
US Referenced Citations (16)