氧化锌压敏陶瓷伏安特性的微观解析

为从微观层面上解析ZnO压敏陶瓷MOV的宏观伏安特性,根据电镜和深能级瞬态谱(DLTS)的观测结果,结合试验实测几种规格MOV小电流和大电流下的试验数据,建立ZnO在小电流区和大电流区的微观集中参数等效电路模型,然后依据晶界势垒、电子陷阱等理论,微观解析了各区的导电特性。结果表明:随着外施电压的增加,电子的穿透能力不断增强,使ZnO在小电流区晶界层的非线性微观等效电阻不断增大,它与纯ZnO晶粒层的线性电阻共同作用使ZnO小电流区伏安特性呈现出3个不同的特性宏观区域即预击穿区、击穿区和回升区;随着外施瞬态冲击大电流幅值的加大,ZnO在大电流区微观等效电感值增加,使ZnO大电流区伏安特性宏观呈现缓慢上升区、快速上升区和迅速上翘区;晶界层厚度的不均匀性和晶界层中电子陷阱密度的差异性宏观表现为等效电阻的非线性变化,晶界层和纯ZnO晶粒层在小电流区和大电流区具有不同的微观作用机理使得ZnO压敏陶瓷在不同电流区呈现出不同的独特宏观伏安特性。

Microcosmic Analysis of U-I Characteristic of ZnO Pressure-sensitive Ceramics

The U-I characteristic of ZnO pressure-sensitive ceramics is analyzed, ZnO pressure-sensitive ceramics consists of grain crystal with different size, which is polygonal crystal. The U-I characteristic of ZnO pressure-sensitive ceramics consists of three area: the beforehand-breakdown area, the breakdown area and the rise area. The beforehand-breakdown area is linear nearly. The breakdown area is nonlinear, ZnO pressure-sensitive ceramics is used in this area. The nonlinearity of ZnO pressure-sensitive ceramics is worse in the rise area. The established original microcosmic model in low current and high current area is observed with electron microscopy and analyzed. U-I characteristic in the low current area is presented through experiment of actual several kind of specification MOV in the D.C. voltage according to microscopic model and grain boundary barrier and electronic trap theories. In low current area, the nonlinear resistance can not participate in the procedure of the electric conduction when the voltage is very low, and the U-I characteristic of ZnO pressure-sensitive ceramics is linear nearly. With increase of the voltage , the nonlinear resistance participates in the procedure of the electric conduction little by little,and the ZnO pressure-sensitive ceramics presents nonlinear. In the high current area, the inductance and the variety of the current are decisive factors. The electric conduction characteristic of various sectors has analyzed by electron microscopy, equivalent resistance of grain boundary layer is increased slowly due to asymmetry thickness of grain boundary layer and electron trap density in grain boundary layer,different electric mechanism of grain boundary layer and pure grain of ZnO brings up unique U-I characteristic of ZnO Pressure-sensitive Ceramics.