Electron traps in zinc-oxide varistors

Admittance spectroscopy was used to characterize the bulk electron traps present in commercial ZnO varistors, the ZnO-BiIn the ZnO-BiSmall amounts of dopants were added to the ZnO-BiThere is evidence that the pulse response characteristics of the primitive zinc oxide varistors have a material origin. The inductive behavior of a device is suggested to originate from bulk traps. This behavior can be controlled by doping. Additionally, the electronic defects variations are found to be related to the nonlinear exponents of a varistor, which can be possibly connected to the breakdown mechanism.Three types of commercial varistors were examined. Though there are variations in the spectra shapes, two traps with energies of 0.17 and 0.33 eV below the conduction band edge were found in all three types. Chemical element differences and different processing conditions are suspected as the cause of the spectra shape variation. The complexity of the chemical compositions makes it difficult to know the origin of traps.