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Method of processing "BPS" glass ceramic and seals made therewith

United States Patent

*** EXPIRED ***
5,820,989
October 13, 1998
View the Complete Patent at the US Patent & Trademark Office
Sandia National Laboratories - Visit the Intellectual Property Management and Licensing Website
A glass ceramic composition, a glass ceramic-to-metal seal, and more specifically a hermetic glass ceramic-to-metal seal prepared by subjecting a glass composition comprising, by weight percent, SiO.sub.2 (65-80%), LiO.sub.2 (8-16%), Al.sub.2 O.sub.3 (2-8%), K.sub.2 O (1-8%), P.sub.2 O.sub.5 (1-5%), B.sub.2 O.sub.3 (0.5-7%), and ZnO (0-5%) to the following processing steps: 1) heating the glass composition in a belt furnace to a temperature sufficient to melt the glass and crystallize lithium phosphate, 2) holding at a temperature and for a time sufficient to create cristobalite nuclei, 3) cooling at a controlled rate and to a temperature to cause crystallization of lithium silicates and growth of cristobalite, and 4) still further cooling in stages to ambient temperature. This process produces a glass ceramic whose high coefficient of thermal expansion (up to 200.times.10.sup.-7 in/in/.degree.C.) permits the fabrication of glass ceramic-to-metal seals, and particularly hermetic glass ceramic seals to nickel-based and stainless steel alloys and copper.
Reed; Scott T. (Albuquerque, NM), Stone; Ronald G. (Albuquerque, NM), McCollister; Howard L. (Albuquerque, NM), Wengert, deceased; Paul R. (late of Albuquerque, NM)
Sandia Corporation (Albuquerque, NM)
08/ 706,852
September 3, 1996
This invention was made with Government support under Contract No. AC04-76DP00789 awarded by the United States Department of Energy. The Government has certain rights in the invention.