Admittance Spectroscopy of Polycrystalline ZnO-Bi2O3 and ZnO-BaO Systems

Admittance spectroscopy was used to characterize the bulk electron traps in polycrystalline ZnO‐Bi2O3 and ZnO‐BaO systems. Temperatures from 30 to 350 K and a frequency range from 1.0 to 33.3 kHz were used. Admittance spectra for the ZnO‐Bi2O3 system showed large variations with sintering atmosphere and heat treatment. A trap is observed at 0.33 eV below the conduction band edge in both systems. This trap is likely to be associated with an ionized oxygen vacancy. A possible explanation of primitive varistor characteristics in terms of the roles of the electronic defects is presented.