脉冲电场下ZnO压敏陶瓷动态击穿过程研究

陶瓷电击穿问题涉及热、光、电多场耦合效应, 一直是非平衡物理学研究的重点和热点。本工作在不同烧结温度下制备了晶粒尺寸大小不同的氧化锌陶瓷, 采用脉冲高压发生装置对陶瓷进行击穿实验, 通过对陶瓷击穿过程的分析和对比, 研究了ZnO陶瓷体击穿的时间步骤。结果显示, 不同晶粒大小的陶瓷击穿过程均在7 μs之内, 典型的压降曲线分为三个阶段。第一个阶段对应于材料中的气孔击穿和击穿通道初步形成; 第二阶段对应于晶界击穿; 第三个阶段是导电通道的完全形成。研究数据显示, 晶粒击穿过程的持续时间最长, 晶界次之, 气孔的击穿时间最短。不同烧结温度下, 样品晶界和晶粒的击穿时间以及气孔的击穿速度均存在差异。

Dynamic Breakdown of ZnO Varistor Ceramics under Pulsed Electric Field

Electrical breakdown process of ceramics is a complex process related to electrical, thermal, and light effects. It has attracted lots of attentions. But the mechanism of dielectric breakdown is still under debate, especially for the solid ceramics. In this study, the ceramics with different grain size were sintered at different temperatures. A square pulsed voltage of 27 kV with the pulse width of 7 ms was generated to breakdown the ZnO ceramics with a thickness of 2 mm. Electric breakdown process of these ceramics were investigated using a homemade high-time- resolution electric detection system with the resolution < 1 ns. Compared the electric behaviors of ZnO ceramics with different grain sizes during the breakdown process, it is clear that the whole electric breakdown process could be divided into three main steps, all of which can completed within 7 ms. The first breakdown step is the pores breakdown due to the electric field concentration, and the second step is the grain boundaries breakdown, and then the bulk grain is broken-down leading to form the whole electrical breakdown channel. The data shows that the breakdown process of the grains has the longest duration, the grain boundary is the second, and the pores breakdown is the shortest. For the ceramics with different grain sizes, the breakdown durations of the grain boundaries are different. The duration and electrical breakdown speed of the three step processes are directly affected by the resistance uniformity and carrier concentration of the materials.