Features of the Design and Technology of Cylindrical Sapphire Soldering with Metals Used in Gas-Discharge Lamps

Abstract

The article considers the design and technology features of cylindrical soldering of sapphire (corundum) with niobium and kovar alloy (alloy 29NK), developed for use in flash lamps with a discharge in alkali metal vapors. The performance of a gas-discharge lamp is analyzed and the basic requirements for the junctions are determined. The main types of defects determining the optical transparency and mechanical strength of a corundum monocrystal grown by directional crystallization the Stepanov method are shown, and the main requirements for a profiled sapphire tube are formulated. The results of internal stresses reduction studies during heat treatment of a corundum pipe before soldering are presented. The special attention is paid to the study of physicochemical phenomena occurring in the process of soldering sapphire with niobium using glass-ceramic solder and with kovar copper. It is proved that for the soldering corundum with niobium it is necessary to introduce up to 1 % zirconium impurity into the metal structure, which allows reducing the recrystallization of the alloy and decreasing the migration rate of the formed grains. In the case of active soldering sapphire with kovar, the importance of observing the recommended temperature regimes for melting solder to prevent the formation of titanium intermetallic compounds is shown. The main design solutions of sapphire soldered joints and the results of their tests for resistance to mechanical and climatic factors are given

Please cite this article in English as:

Gavrish S.V., Puchnina S.V. Features of the design and technology of cylindrical sapphire soldering with metals used in gas-discharge lamps. Herald of the Bauman Moscow State Technical University, Series Instrument Engineering, 2022, no. 2 (139), pp. 96--111 (in Russ.). DOI: https://doi.org/10.18698/0236-3933-2022-2-96-111

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