| 摘要 |
<p>A vacuum-tight assembly, such as a discharge tube (10) for a sodium vapor arc lamp, includes a high density polycrystalline ceramic body, such as alumina or yttria, having a cavity (12) and at least one closure member (14) and a sealing material (24) for sealing the cavity (12) from the atmosphere. The closure member (14) is formed from a molybdenum alloy containing titanium, vanadium, chromium or mixtures thereof. The closure member (14) and the sealing material (24) have thermal coefficients of expansion closely matched to the thermal coefficient of expansion of the ceramic body over a wide temperature range. In a preferred embodiment, an alumina discharge tube (10) is sealed by a closure member (14) formed from a molybdenum alloy containing 50 atom percent titanium.</p> |
