Alumina is widely used as a vacuum ceramic separator in the pillbox-type output window of high-power electron tubes. The fracture of alumina is one of the most important factors in the failure of these tubes. In this article, the fracture process of alumina in the pillbox-type window of high-power electron tubes is assessed microscopically. The investigation shows the twinning phenomenon in the fractured alumina. The reason for initiating and propagating twins is also investigated. An increase in the alumina temperature decreases the required stress level for generating twins. The overheating condition occurs due to an impedance mismatch in the pillbox-type window. Experimental and numerical analyses are presented to verify the mechanism of mechanical stress due to the overheating condition. The numerical analysis is carried out by the finite-element method (FEM). The result of this study can provide information for proposing a temperature monitoring scheme to turn off the tube before reaching the overheating condition.

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大功率电子管药盒型RF窗口中氧化铝断裂的微观评估

氧化铝在大功率电子管的药盒型输出窗口中被广泛用作真空陶瓷隔板。氧化铝的断裂是这些管失效的最重要因素之一。在本文中，用显微镜评估了氧化铝在大功率电子管药盒型窗口中的断裂过程。研究表明，在断裂的氧化铝中存在孪生现象。还研究了引发和繁殖双胞胎的原因。氧化铝温度的升高降低了产生孪晶所需的应力水平。由于药盒类型窗口中的阻抗不匹配而导致出现过热情况。进行了实验和数值分析，以验证由于过热条件引起的机械应力的机理。数值分析是通过有限元方法（FEM）进行的。这项研究的结果可以为提出一种温度监测方案以在达到过热状态之前关闭管子提供信息。