With the system of ZnO+MgO+Al₂O₃+SiO₂, zinc oxide (ZnO) linear resistors were prepared. The effects of calcination conditions of the ZnO ceramic powder and sintering temperature of the ceramic body on temperature coefficient and resistivity of the ZnO ceramic linear resistors were studied. When the ZnO powder was calcined at 1000 ℃ and the ceramic body was sintered at 1240 ℃, the resistivity of the resistor reached 1165 Ω·cm. Additionally, at a testing temperature of 100 ℃, the temperature coefficient of the ZnO linear resistors initially increased and then decreased with increasing resistivity. Moreover, the primary raw material ZnO in the ceramic powder, after calcination, resulted in a lower temperature coefficient of linear resistance. Specifically, when the ZnO was calcined at 800 ℃ and the ceramic body was sintered at 1240 ℃, temperature coefficient of the resistors achieved the lowest value at 520 ppm·℃^-1.

The effects of aluminum indium codoping on the microstructure and electrical properties of ZnO varistors, especially the surge impact stability, were studied. The microstructure was characterized by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrical properties were evaluated by using current-voltage test, pulsed current impulse test and capacitance-voltage test. The sample doped with 0.0008 mol% Al³⁺ and 0.0033 mol% In³⁺ exhibited excellent electrical properties, with breakdown voltage gradient of 95.3 V·mm⁻¹, nonlinear coefficient of 74 and residual voltage ratio of 2.43. In addition, after 20 shocks at 8/20 μs 10 kA current, the positive and negative voltage change rates were +3.30% and −6.67%, respectively.