Dependence of the nonlinear electrical behavior of SnO_2-based varistors on Cr_2O_3 addition

摘要

Tin dioxide varistors doped with CoO, ZnO, Ta_2O_5 and Cr_2O_3 were prepared by the mixed oxide method. Temperature dependent impedance spectroscopy revealed two different activation energies, one at low frequencies and the other at high frequencies. These activation energies were associated with the adsorption and reaction of O_2 species at the grain boundary interface. We show that Cr_2O_3 improves the varistor properties, generating sites for the adsorption of O' and O" at the grain boundary region. The O' and O" defects are truly responsible for the barrier formation at the grain boundary interface.