Element doping is an effective method to improve the performance of ZnO varistors. Previous studies mainly focused on the variation of microstructures and Schottky barriers. In this study, the effects of Co dopant on electrical properties are investigated from the aspect of multiscale defect structures, including intrinsic point defects, the heterogeneous interface of depletion/intergranular layers, and interface states at grain boundaries. Combining with analysis of phase composition and energy dispersive spectroscopy, it is found that Co tends to dissolve into ZnO grains when slightly doped. It substitutes Zn2+ with the same valence and affects little on densities of donors. Segregation of Co at grain boundaries would result in the formation of spinel phase Co(Co4/3Sb2/3)O4 and transformation of the intergranular phase from α-Bi2O3 to δ-Bi2O3. Meanwhile, densities of point defects are indirectly affected by oxygen ambient during sintering, resulting in abnormal variation of grain resistivity. And interface states are enhanced, leading to improved barriers at grain boundaries. Therefore, reduced leakage current, enhanced grain resistivity, and improved non-linear coefficient in Co-doped ZnO varistor blocks are understood from the underlying multiple defect structures. This presents a potential approach to explore short-term performance and long-term stability of ZnO varistors from the aspect of defect responses.

中文翻译：

---

回顾Co2O3对ZnO压敏电阻多尺度缺陷结构和相关电性能的影响

元素掺杂是提高ZnO压敏电阻性能的有效方法。先前的研究主要集中于微观结构和肖特基势垒的变化。在这项研究中，从多尺度缺陷结构（包括本征点缺陷，耗尽/晶间层的异质界面以及晶界处的界面状态）的角度研究了Co掺杂物对电性能的影响。结合相组成分析和能量色散光谱分析，发现当轻度掺杂时，Co倾向于溶解在ZnO晶粒中。它以相同的化合价取代Zn2 +，对施主的密度影响很小。Co在晶界处的偏析会导致尖晶石相Co（Co4 / 3Sb2 / 3）O4的形成以及晶界相从α-Bi2O3转变为δ-Bi2O3。同时，烧结过程中氧环境间接影响点缺陷的密度，导致晶粒电阻率异常变化。界面状态得到增强，从而改善了晶界处的势垒。因此，从潜在的多个缺陷结构中可以看出，Co掺杂的ZnO压敏电阻块中的漏电流减小，晶粒电阻率提高，非线性系数提高。这提供了一种从缺陷响应角度探讨ZnO压敏电阻的短期性能和长期稳定性的潜在方法。从底层的多个缺陷结构中可以看出，Co掺杂的ZnO压敏电阻块具有增强的晶粒电阻率和改善的非线性系数。这提供了一种从缺陷响应角度探讨ZnO压敏电阻的短期性能和长期稳定性的潜在方法。从底层的多个缺陷结构中可以看出，Co掺杂的ZnO压敏电阻块具有增强的晶粒电阻率和改善的非线性系数。这提供了一种从缺陷响应角度探讨ZnO压敏电阻的短期性能和长期稳定性的潜在方法。