Evaluation of Sb2O3-Doped ZnO Varistors by Photoacoustic Spectroscopy

Abstract

Photoacoustic (PA) spectra for the Sb2O3-doped ZnO varistors were measured to study the Sb2O3 doping effects on their nonradiative properties and deep levels, where the Sb2O3-doped ZnO varistors had the highly nonohmic current-voltage feature. For the samples without the Sb2O3 doping, the PA spectra are almost flat between 750 nm and 950 nm. When the ZnO varistors were doped with Sb2O3, a decrease in the intensities of the PA signals above 800 nm with increasing wavelength is observed. The Sb2O3 doping generates the spinel phase, which suppresses the concentration of Co dissolution into the ZnO grains; the PA peaks of Co in ZnO observed between 800 nm and 1000 nm appear to be low. The small peak at approximately 950 nm is observed for the Sb2O3-doped samples. This peak corresponded to the deep level caused by the Sb2O3 doping. The analysis of this level helps in the estimation of the properties of ZnO varistors.