Effect of BaTiO3 Doping on the Surface Insulation Properties of Alumina in SF6 Under DC Voltage

Ceramic materials have high mechanical strength, excellent temperature stability and aging resistance. Compared with epoxy resin, it is more suitable for the alternative material solutions of surface insulation in complex working conditions of strong electric field and large temperature gradients. However, there is still a certain distance between the surface insulation performance of alumina-based ceramic insulation materials used in the field of external insulation of power industry and the actual requirements of internal insulation pillars for UHVDC equipment, and its key electrical properties need to be regulated. Therefore, a new type of Al
2
O
3
/BaTiO
3
composite ceramic material was prepared by using ion doping technology in this paper. It is found that the electrical properties of ceramics doped with 3% BaTiO
3
are excellent. The volume resistivity at room temperature is
$2.01\times 10^{15}\Omega\cdot \mathrm{m}$
, and the average surface charge density under positive and negative DC voltages is 0.43 pC/mm2 and 0.42
$\text{pC}/\text{mm}^{2}$
, which is 32.59% and 27.40
^%
lower than that of pure alumina ceramics, and the flashover voltage is 19.15% higher than that of pure alumina ceramics. Doping Ba
²
+ with high ionic radius will hinder the movement of weakly bound carriers, increase the conduction barrier, thereby increasing the volume resistivity, slowing down the migration rate of internal carriers, and reducing the charge from solid to gas-solid surface, thereby inhibiting the accumulation of surface charge, and weakening the distortion of local electric field on the surface, thereby increasing the flashover voltage to a certain extent. The research results provide a theoretical basis for the regulation of surface insulation properties of ceramics in SF6 under DC voltage by ion doping based on large ion suppression effect.