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ZnO-based varistors have been widely applied in surge protection devices because of their excellent nonlinear current-voltage (I-V) characteristic and energy absorption ability. Manganese is always added into ZnO-based varistors in order to enhance the nonlinear characteristic of materials. In the present work, the dielectric properties of Mn-doped ZnO-Bi2O3 varistors at extremely low temperatures...
The interior distributions of electrical and dielectric properties of ZnO varistor at initial aging stage are investigated. Two commercial varistors at different aging stages were compared. These two varistors were cut into slices along the axial direction, and then the variations of varistor slices' electrical and dielectric performances were obtained. The results show that the interior performance...
ZnO varistors have been extensively used against transient surges because of the excellent nonlinearity. ZnO varistors are obtained by sintering semiconducting ZnO powder with small amount of metal oxide additives. Amongst, Mn-doping is effective in the enhancement of the nonlinearity. In this paper, the relationship between the microstructure, the electrical and dielectric properties of Mn-doping...
ZnO-based varistors have been extensively used for the protection of devices and equipment against voltage surges because of their exceptional nonlinearity in current-voltage characteristics and the ability to absorb large amounts of energy. Since the composition and fabrication process are complicated, impurities are inevitable in the varistors. Sodium impurities are frequently present in the raw...
ZnO varistors are used extensively as the surge suppressor in the form of surge arresters in the power protection against lightning, temporary over-voltages, switching surges, transients, etc. In this research, DC degradation process at 50 mA/cm2 for 115 hours and restorability by heat-treatment at 800 oC for 24 hours for ZnO varistors were performed. The breakdown field E1mA (electric field at 1...
The electrical and dielectric properties of a commercial ZnO-based varistor ceramics were measured in the process of 8/20mus impulse current degradation with a current density of 1725A/cm2. The characteristic of U-I in the pre-breakdown region was mainly investigated. It was found that the varistor voltage U1mA will first increase rapidly with the times of impulse, and then remain stable and finally...
In this paper, ZnO varistor+Al2O3 ceramic+ZnO varistor insulators were made, in which the conductivity and permittivity of ZnO varistors were controlled by changing its voltage gradient. Then the influences of conductivity and permittivity of ZnO varistors on the DC and pulsed surface flashover voltage in vacuum were experimentally investigated. The experimental results indicated that the DC and pulsed...
The effect of two Ag electrodes on the electrical properties of SrTiO3 ring varistors were presented in this paper. It was found that one of them results in ohmic contact while the other results in non-ohmic contact between electrode and ceramics. Compared with the results achieved by using of In-Ga alloy paste, non-ohimic contact lead to larger varistor voltage U10mA, larger nonlinear coefficient...
The influence of magnetized water on the electrical properties of ZnO varistor ceramics was investigated by electrical property measurement and frequency spectrum technology. It was found that, compared with results of deionized water, higher varistor voltage E1mA and lower non-linear coefficient alpha can be achieved by using 0.2 T magnetized water, while E1mA and alpha of 0.3T magnetized water are...
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