Effect of Aluminum Nitride on Discharge Mode Transition in Atmospheric Pressure He/O2 DBD

In this paper, the effects of aluminum nitride and alumina ceramics on the discharge mode of He/O
₂
mixed gas are studied and compared. It is found that when the O
₂
volume fraction is in the range of 0.2%-1%, dielectric barrier discharge (DBD) with Al
₂
O
₃
is always in the unstable filamentary mode, and homogeneous and filamentary modes are observed in DBD with AlN. Under the homogeneous discharge mode, there is only one current pulse each half-voltage cycle, and the intensified charge-coupled device discharge image shows that it is glow discharge. The relative permittivity and surface charge decay characteristics of AlN and Al
₂
O
₃
are measured. The experimental results show that the relative permittivity of AlN is lower than that of Al
₂
O
₃
, but its surface charge decay is obviously slower than that of Al
₂
O
₃
. The derived electron trap density from the surface charge decay of AlN ceramic is higher than that of Al
₂
O
₃
, which shows AlN has a strong charge capacity and can emit more electrons in the second half cycle of the discharge. The higher secondary electron emission coefficient can make the discharge ignition voltage lower and the formation of stable homogeneous discharge easier. This paper provides a new control method for expanding homogeneous discharge in He/O
₂
mixed gas.