Influence of coating to surface flashover characteristics of alumina ceramics in vacuum

Alumina ceramics are widely used for vacuum insulation in devices such as vacuum interrupters. In development and design of vacuum interrupters, it is very important to improve the flashover characteristics on alumina ceramic surfaces in vacuum. Thus, it is necessary to clarify the flashover mechanism on alumina ceramics in vacuum. From past research, it is well-known that these characteristics are influenced by the insulation material, its surface condition, surface charging of the insulator and so on. This paper presents the results of measurements of surface flashover characteristics and observation of the surface and cross-section surface of Al
₂
O
₃
coated Cr
₂
O
₃
by SEM. These results are compared with those without coated Cr
₂
O
₃
. It is thus found that Cr
₂
O
₃
coating decreased the surface resistance and improved the surface flashover characteristics of Al
₂
O
₃
in vacuum.