Effect of Cr2O3 coating sintered at high temperature on the vacuum surface hold-off voltage performance of Al2O3 ceramic
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摘要: 利用浸涂法将Cr2O3涂覆于Al2O3陶瓷表面,通过高温烧结获得涂层陶瓷,并系统性地研究了Cr2O3涂层对样品的物质成分、微观形貌、二次电子发射系数、表面电阻率和真空沿面耐压性能的影响。结果表明:涂层陶瓷表面呈红黑色,其为Al2O3-Cr2O3固溶体、MgAl2O4和Cr2O3三种物质的混合物。相较于Al2O3陶瓷,涂层表面晶粒和孔洞的尺寸均较小,其晶粒尺寸均匀性也有明显提升。高温烧结后,Al、Cr两种元素相互扩散,并且涂层中有少量从陶瓷基体迁移而来的玻璃相。高温烧结的Cr2O3涂层将Al2O3陶瓷的二次电子发射系数减小至3.22,将表面电阻率减小至4.52×1011 Ω,将真空沿面耐压强度增大至34.44 kV/cm,此值较Al2O3陶瓷提高了约108%。Abstract: In this study, Cr2O3 was applied to the surface of Al2O3 ceramic via a dip-coating method. Subsequently, the final coated ceramic was obtained through high-temperature sintering. The effects of the Cr2O3 coating on material composition, microstructure, secondary electron emission coefficient, surface resistivity, and vacuum surface hold-off voltage performance were systematically investigated. The results indicate that the surface of the coated ceramic appears dark red, representing a mixture of three materials: Al2O3-Cr2O3 solid solution, MgAl2O4, and Cr2O3. Compared to the Al2O3 ceramic, both the grain size and pore size on the surface are reduced, and the homogeneity of the grain size is significantly enhanced. After high-temperature sintering, Al and Cr diffuse into each other. Additionally, a small amount of glass phase, likely migrating from the ceramic substrate, is detected in the coating. Owing to the high-temperature sintering of the Cr2O3 coating, the secondary electron emission coefficient is reduced to 3.22, and the surface resistivity is also lowered to 4.52×1011 Ω. Furthermore, the vacuum surface hold-off electric field strength of the coated ceramic increases to 34.44 kV/cm, which is approximately 108% higher than that of the Al2O3 ceramic.
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表 1 陶瓷样品的表面成分
Table 1. Surface ingredient of ceramic samples
sample mass fraction/% O Na Mg Al Si K Ca Cr Al2O3 ceramic 40.8 0.5 0.54 56.06 0.67 0.53 0.89 / Cr2O3 coated Al2O3 ceramic 33.54 / 0.19 18.73 0.52 / 0.03 46.99 -
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