Effects of Cr2O3 addition on microstructure and vacuum flashover performance of glass-ceramics

K₂O-MgO-SiO₂-Al₂O₃-B₂O₃-F/Cr₂O₃ glass-ceramics with higher flashover voltage were fabricated by sintering method. The electrical properties were measured, it was found that the flashover voltage was improved obviously with addition of small amount of Cr₂O₃. The crystalline phases were identified by XRD and the microstructures were observed by SEM and BSE, the results showed that, there were Cr₂2O₃ "islands" existed on the surface of ceramics. These "islands" could absorb the secondary electron and form the secondary electron "black hole". The electric field distribution on surface was also simulated based on BSE and SEM results by ANSYS, it was showed that the Cr₂O₂ "islands" also distorted the surface electrical field. Therefore, the flashover voltage was increased. When adding with 3wt% Cr₂O₃, the hold-off voltage of glass-ceramics reached to 57 kV cm-1 (improved by 45%).