Effect of Sb2O3 addition on the varistor characteristics of ZnO-Bi2O3-ZrO2-MtrO (Mtr = Mn, Co)

Effect of Sb2O3 addition on the varistor characteristics of pyrochlore-free ZnO-Bi2O3-ZrO2-MtrO (M-tr = Mn, Co) system previously proposed has been studied. With Sb2O3 up to 0.1 mol%, a gradual enhancement of densification and the grain growth inhibition were seen in the system sintered between 900 and 1200 degrees C. In X-ray diffraction patterns, small amount of pyrochlore appeared in the specimens doped with Sb2O3 (> 0.06 mol%), which is thought responsible for the sintering behavior. Enhanced values of non linear coefficient (alpha) were obtained in ZnO-Bi2O3-ZrO2 (ZBZ) doped with 0.001 mol% Sb2O3, but was leveled off at higher concentrations. In ZBZ added with MtrO (M-tr = Mn, Co), significant increase of nonlinear coefficient (alpha > 30) along with low leakage current (I (L) << 100 mu A/cm(2)) was attained. The alpha-enhancement effect of Sb2O3, however, was not observed in high-alpha ZBZ added with MtrO. As for degradation, addition of a trace amount (0.001 mol%) of Sb2O3 to ZBZM(tr) was efficient, especially in I (L).