Effect of capacitance on ZnO-Bi₂O₃-Yb₂O₃ based varistor for nanosecond transients

Abstract

The microstructure and electrical properties of ZnO-ZnO-Bi₂O₃-Yb₂O₃ based varistor ceramics were investigated with various temperature effects from 900 °C to 1050 °C. From the results, it was observed that the increase of sintering temperature offers a reduced capacitive effect from 0.460 nF to 0.321 nF. Furthermore, the grain sizes of varistors were varied from 6.8 μm to 9.8 μm. The consequence of such smaller grain sizes provided a better voltage gradient of about 895 V/mm for the disc sintered at 900 °C and fallen drastically to 410 V/mm for the sample sintered at 1050 °C. In addition, there was an increase of non-linearity index to a maximum value of 36.0 and reduced leakage current of 0.026 mA/cm². However, the density of the varistor decreased with an increase of temperature from 5.41 g/cm³ to 5.24 g/cm³. With this base, the influence of varistor capacitance and high voltage gradient were scrutinized and it led an improved transition speed of the varistor assembly from non-conduction to conduction mode during intruding nanosecond transients.

摘要

研究了 ZnO-Bi₂O₃-Yb₂O₃ 基压敏陶瓷在 900 °C 至 1050 °C 温度范围内的显微组织和电学性能变化。 结果表明, 随着烧结温度的升高, 电容效应从 0.460 nF 降低到 0.321 nF。 此外, 压敏电阻的晶粒大小从 6.8 μm 增大到 9.8 μm。 这种小的晶粒使样品在 900 °C 烧结时获得更好的电压梯度, 约为 895 V/mm, 而当烧结温度升高到 1050 °C 时, 电压梯度迅速下降到 410 V/mm。 另外, 非线性指数增加到最大值 36.0, 泄漏电流减少到 0.026 mA/cm²。 然而, 随着温度的升高, 压敏电阻的密度从 5.41 g/cm³ 降低到 5.24 g/cm³。 在此基础上, 考察了压敏电阻电容和高压梯度的影响, 从而提高了压敏电阻组件在侵入纳秒瞬态下从非导电态转变到导电态的转变速度。