Electric behaviour of ZnO varistor studied from TSC measurement

In this paper, the results of the ZnO varistor voltage-current characteristics and the thermally stimulated current (TSC) components separated in the temperature range from 50 to 340 K are reported. Additionally, some experimental results before and after applying high-voltage impulse (10 kV) as a false load are reported and discussed. From the experiments on the TSC of ZnO varistor, the following results were obtained: (1) some TSC curves (four or six) of the first-order that correspond to the discrete state individually in the grain boundary can be separated in the temperature range from 50 to 340 K. (2) The dominant TSC peak appeared around room temperature. The trap depth, Et, of this peak depends on the poling field Ep. As Ep increases, Et increased from ca. 0.31 to 0.38 eV. (3) The ν value for the dominant TSC peak varied from ca. 10² to 10³ 1/s. (4) From this detailed study on the ν value of traps, it is understood that the varistor effect depends on the ν value of the dominant TSC peak