Cr2O3 doping in ZnO–0.5mol% V2O5 varistor ceramics

Abstract The effects of the amount of Cr 2 O 3 (0.5–4 mol%) on the microstructure and the electrical properties have been studied in a binary ZnO–0.5 mol% V 2 O 5 system. The microstructure of the samples consists mainly of ZnO grains with ZnCr 2 O 4 and α-Zn 3 (VO 4 ) 2 as the minority secondary phases. The addition of Cr 2 O 3 is found to be effective in controlling the abnormal ZnO grain growth often found in V 2 O 5 -doped ZnO ceramic system, and a more uniform microstructure can be obtained. The varistor performance is also improved as observed from the increase in the non-linear coefficient α of the Cr 2 O 3 -doped ZnO–V 2 O 5 samples. The α value is found to increase with the amount of Cr 2 O 3 for up to 3 mol% Cr 2 O 3 content. Further increase in Cr 2 O 3 is found to cause a decrease in the α value. The highest α value of 28.9 is obtained for the ZnO–0.5 mol% V 2 O 5 –3 mol% Cr 2 O 3 sample.