Preparation and characterisation of Sb2O3 with or without Cr2O3 and CoO containing ZnO varistors

Abstract Zinc oxide samples with different contents of Sb2O3 with or without Cr2O3 and CoO have been prepared by conventional ceramic processing for use as varistors. Reaction sintering was performed at 1200 and 1300°C. X-ray studies indicate that the mixtures contained mainly zincite phase together with two different chemical formulas of spinel-like structure, β-Zn7Sb2O12 and Zn2.33Sb0.67O4, at 1200 and 1300°C respectively. ZnCr2O4 and CoCr2O4 were also formed as spinel-like structures besides Zn2.33Sb0.67O4 and zincite phase in the mixtures doped with Cr2O3 and CoO at 1200 and 1300°C. Variation in current–voltage (I–V) characteristics is discussed in terms of microstructural and crystallographic changes in the varistors. The addition of Cr2O3 and CoO to the ZnO varistors containing Sb2O3 has been confirmed to be effective in enhancing non-linear behaviour.