Enhancement of Surface Flashover Voltage of 95 Alumina Porcelain in Vacuum Using Cu2O‐Doped Cr Matrix Composite Coating

Abstract

Surface flashover of 95‐alumina electrovacuum devices in high‐voltage vacuum environments can lead to electrical breakdown. In this study, Cr‐based composite coatings with varying Cu2O doping levels (3%–9%) were prepared on 95‐alumina substrates via high‐temperature solid‐phase sintering. The results show that, at a Cu2O doping ratio of 7.5%, the coating exhibits the highest surface porosity, surface roughness (Rq = 0.47 µm, Ra = 0.35 µm), and height difference (3.9 µm), as confirmed by SEM and AFM analysis. Meanwhile, the surface trap characteristics are significantly improved, with deep trap energy level of 0.995 eV and density of 5.32×1020 m−3eV−1. These deep traps can suppress electron injection and capture carriers, thereby reducing carrier mobility by hindering charge transport. Consequently, the surface resistivity decreases to 6.68×1010 Ω. By increasing the deep trap parameters and reducing the surface resistivity, the phenomenon of electron multiplication during the flashover process was effectively suppressed, thereby increasing the 50% surface flashover voltage of 95 porcelain from 43 to 58.7 kV. This study demonstrates that an appropriate amount of Cu2O doping in Cr‐based coatings can significantly enhance surface flashover voltage, providing valuable insight for the application of 95‐alumina porcelain in electrical vacuum insulation.