Electric lamp and discharge devices – With gas or vapor – Envelope composition
Patent
1985-01-10
1986-04-29
McCarthy, Helen M.
Electric lamp and discharge devices
With gas or vapor
Envelope composition
65 43, 156 89, 313624, 313638, 501 9, 501 15, 501 63, 501 64, 501 66, 501 67, 501 69, H01J 6122, H01J 6130, H01J 6136
Patent
active
045859728
ABSTRACT:
An arc discharge lamp is provided using sealing compositions comprising mainly Al.sub.2 O.sub.3 --SiO.sub.2 --MgO. Preferred compositions include between 25 to 28% by weight of MgO and 13 to 21% by weight of Al.sub.2 O.sub.3 since these have lower melting points than others in the group. Additives of B.sub.2 O.sub.3, nucleating agents and HfO.sub.2 and other rare earth oxides are preferred. The sealing compositions are used to seal end closure members of alumina or CERMET to ceramic arc tubes for use in discharge lamps. The compositions are selected to have linear expansion co-efficients compatible with the materials of the end closures and arc tubes. The methods described give scaling times of between 3 and 4 minutes.
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Levin et al.--Phase Diagrams for Ceramists (1969), FIGS. 712, 2530, 2535.
Rankin, G. A. et al.--"The Ternary System MgO--Al.sub.2 O.sub.3 --SiO.sub.2 ", Am. J. of Science, vol. LXV, Apr. 1918, pp. 301-325.
McCarthy Helen M.
Thorn EMI Limited
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