Process for vacuum-tight sealing of a ceramic tube

Abstract

Cylindrical tubes of translucent alumina ceramic, which have metallic current bushings at the ends, are sealed vacuum-tight. For this purpose, a metallizing paste which contains (a) at least one finely dispersed metal powder composed of tungsten, molybdenum, niobium or tantalum, (b) a liquid organic binder and (c) a pulverulent calcium-magnesium silicate having a melting point in the range of 1200.degree.-1500.degree. C., is applied to the ends of the tube, the paste is burned in on the alumina ceramic and a thin metal layer is thus produced, a further layer of nickel or copper is deposited chemically or by electroplating on the metal layer remaining after the burning-in, metallic current bushings are inserted into the tube in the region of the tube ends, and the ends are sealed in the metallized areas by means of a brazing solder having a melting point between 950.degree. and 1200.degree. C., for example a Cu/Ag alloy, if necessary with the use of disk-shaped gasket elements.

Dependencies are inferred from the claim text.