A general aging model of the double Schottky barrier was proposed to unveil the long-term aging behaviors of $\mathrm{Zn}\mathrm{O}$ varistor ceramics, especially for those ones with steadily decreasing power loss. For those samples, the barrier height and electrical properties were even enhanced rather than commonly deteriorated, which were beyond the classic ion migration model. In this paper, inspired by the unique reversible aging of them, interface states are proposed to remain stable in those samples. The major mobile ions, which have been in debate, are further identified to be ${\mathrm{Zn}}_i^{\cdot }$ ions. Based on these assumptions, a quantitative dynamic ion migration-diffusion model is proposed. The calculated power loss steadily decreases with aging time, which well supported our proposal. When the interface states are not combined with those mobile ions, the formation of a “U-shape” ion spatial distribution in depletion layers is found to be responsible for the unique aging phenomena, i.e., a reduction in the depletion layer and interfacial charge, a rise in the depletion layer width, and an increase in the barrier height. However, continuously increasing power loss would be generated if the mobile ions combined with the interface states. Therefore, a general mechanism on the aging of the double Schottky barrier is unveiled that it is a competition process between consumption of the interface states and the dynamics of mobile ions in depletion layers.

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 Zn ²⁺ 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(Co _4/3 Sb _2/3 )O ₄ and transformation of the intergranular phase from α‐Bi ₂ O ₃ to δ‐Bi ₂ O ₃ . 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.

In numerical solutions of Hanai equation widely used in heterogeneous systems, the uncertainty of conductivity at high frequency affects the accuracy of phase parameters results (permittivity and conductivity of components). To overcome this limitation, broadband dielectric spectroscopy of eight groups of silicone rubber (SR) was measured at a frequency from 10 ⁻¹ Hz to 10 ⁵ Hz and at a temperature from 0 °C to −40 °C. An obvious relaxation peak related to the interface between aluminium hydroxide (ATH) and SR was observed and confirmed. Based on the interfacial polarization, phase parameters of ATH and SR were calculated by modified numerical solutions, which was verified by other information. It was found that with the increase of ATH concentration, polarization strength increased and relaxation time decreased, which indicated that the number of charges accumulated at the interface increased in interfacial polarization process and the Debye length of interface decreased. Because of the surface conductivity around ATH, the conductivity of ATH is higher than that of SR. This paper is beneficial for the studies on the interface properties of ATH filled silicone rubber and provides supports for studying the electrical parameters of particles dispersed in continuous medium systems without physical transition or chemical changes with enhanced accuracy.

Many dielectrics exhibit a (polarization) relaxation response when a time-varying electric field is applied. In some frequency bands, the amplitude of the polarization changes rapidly, with a significant dielectric loss; the maxima in the change rate are referred to as relaxation peaks. ZnO varistors exhibit a dielectric response with several relaxation peaks, but the relationship between the relaxation peaks and electrical properties has not been established. To understand this relationship, dielectric spectroscopy measurements of ZnO varistors were conducted in the temperature range of −110 °C to 200 °C in the frequency range of 10 ⁻¹ –10 ⁶ Hz. By changing two important dopants of Bi ₂ O ₃ and Sb ₂ O ₃ , four relaxation peaks, named Peak A , Peak B , Peak C , and Peak D , were detected. It was found that peaks A , B , and D are indispensable for higher nonlinearity and lower leakage current density. The detection of all four peaks implies that ZnO varistors possess excellent electrical properties, that is, a high breakdown field (235.2 V mm ⁻¹ ), nonlinear coefficient (76.2), and low leakage current density (0.065 μ A cm ⁻² ).