氧化铝保护涂层在铷光谱灯中的应用

The Application of Alumina Potective Coating in Rubidium Spectrum Lamp

铷光谱灯(铷灯)是光抽运铷原子钟的关键部件。在长期工作过程中,铷灯内的铷原子通过化学反应和物理扩散与玻璃泡内壁发生相互作用,引起铷量的快速消耗和光谱性能退化,影响铷原子钟的可靠性。以硝酸铝为前驱物,氨水为沉淀剂,硝酸为胶溶剂,用溶胶凝胶法制备了平均粒径约35 nm的勃姆石(γ-AlOOH)溶胶。采用浸涂法在铷灯泡内表面制备了厚度约3μm的透明氧化铝涂层,在可见和近红外范围的平均透过率大于90%。表面形貌观察显示:涂层均匀致密、表面的平整度和连续性较好,且向玻璃基体发生了明显的渗透现象。6个月铷消耗量跟踪测试表明:透明氧化铝涂层对铷和玻璃表面的反应及扩散的阻滞能力较普通特硬玻璃有明显提高,有涂层铷灯的铷量消耗较无涂层铷灯的铷量消耗减少了50%以上。

The rubidium spectrum lamp （Rb lamp） is the critical component of Rb gas cell atomic frequency standard.The interaction of rubidium with the glass and the rubidium reaction with impurities are the two main reasons of rubidium depletion and light degradation after long-term operation.The γ-AlOOH boehmite sol with grain size of 30 nm was prepared by sol-gel method using Al（NO3） · 9H2O and NH3·H2O as raw materials.A transparent nano-aluminum coating,which is fabricated with dip coating in the inner wall of lamp envelope by Sol-Gel method.The thickness of the alumina coating is 3 μm and the average visible and near-infrared light transmission up to 90％.Observations of SEM show that the inner wall of lamp envelope with a dense uniform and continuous coating.After 6 months operation about half of rubidium consumption of the coated lamp compare to the conventional lamp indicates that nano-aluminum coating is an effective barrier layer for blocking the interaction of rubidium with the glass and reaction with impurities.