SnO2-based varistors capable of withstanding surge current

Electrical properties of new tin dioxide varistor ceramics at high currents

“…15,16,26 The starting compositions are shown in Table 1. The SnO 2 powder (purity of 99.5%) was blended with additives and ball milled in distilled water.…”

“…[11][12][13][14] Recently, the results of the current-voltage characteristics of the SnO 2 -based ceramic varistors test with high-current pulses were reported. [15][16][17][18] The grain resistivity is closely related to the high-current performance of varistor materials. Earlier high values of the grain resistivity in SnO 2 -based ceramic varistors have been reported.…”

“…15,16,26 The grain resistivity (1.2-2.2 ohm cm) in the SnO 2 -CoO-Nb 2 O 5 -Cr 2 O 3 -Y 2 O 3 system was estimated from high-current pulse data. 26 In this paper, new dense varistor ceramics in the SnO 2 -CoO-Nb 2 O 5 -Cr 2 O 3 -Y 2 O 3 -SrO-MgO system are presented, and their behaviour in the high current region is studied.…”

Dependence of residual voltage ratio behavior of SnO2-based varistors on Nb2O5 addition

“…Bueno et al reported that the thermal conductivity of the SnO 2 -based varistor system was two times higher than that of the ZnO-based varistor [12]. It is inferred that, when surge energy was injected into the tested specimens, higher thermal conductivity could improve the temperature uniformity of the ceramic materials and reduce the probability of the thermal-mechanical failure [13], this will also improve their impulse energy absorption capability. In addition, several advantages have been reported for the SnO 2 -based varistors over the ZnO-based varistors [14], such as lower additive contents, higher threshold electric field, higher refractivity and better mechanical properties.…”

“…For this reason, it is expected that a good varistor device should have lower residual voltage ratio. Generally, the residual voltage ratio of commercial ZnO-based varistors is about 1.7, while the value of most SnO 2 -based varistors is more than 2 [13]. If the residual voltage ratio can be lowered further by composition optimizing or new manufacture process, the withstanding capability of the SnO 2 -based varistors to surge current will increase correspondingly.…”