To apply frequency-domain dielectric spectroscopy technology（FDS） to the non-destructive diagnosis of ZnO varistor’ s aging state

impulse aging treatment of ZnO varistor was conducted

and the frequency-domain spectra of the sample with different impulse times were obtained in laboratory environment.The multi-relaxation ColeCole model with DC conductance was introduced to analyze the frequency-domain spectra of the ZnO varistor.The double relaxation Cole-Cole model was used to fit th

e frequency-domain spectra

which were measured at room temperature.It was found that there were a and β relaxation processes with the activation energy about 0.68 and 0.34 e V

which related to the intergranular phase in Bi-rich microregions and the oxygen vacancy respectively.The intensity ofα relaxation process increased with aging

while β relaxation process kept stable.A new y relaxation process with the activation energy about 0.73 eV was observed at the temperature about 393 K.The y relaxation process related to the interface states due to ZnO-ZnO homojunction

and as the impulse times increased

its activation energy and relaxation time decreased

but its relaxation intensity and shape parameter increased.With the increase of the impulse times

the DC conductivity increased obviously

and the activation energy dropped from 0.72 to 0.64 eV.Therefore

the aging status of ZnO varistor can be assessed comprehensively through activation energy of DC conductance

activation energy of y relaxation process

as well as σ

DC

△ε

α

△ε

γ

τ

γ

and γ

which are extracted from the modified multirelaxation Cole-Cole model.