Microstructure and Nonohmic Properties of SnO(2)-Ta(2)O(5)-ZnO System Doped with ZrO(2)

The microstructure and nonohmic properties of SnO(2)-Ta(2)O(5)-ZnO varistor system doped with different amounts of ZrO(2) (0–2.0 mol%) were investigated. The proposed samples were sintered at 1400°C for 2 h with conventional ceramic processing method. By X-ray diffraction, SnO(2) cassiterite phase was found in all the samples, and no extra phases were identified in the detection limit. The doping of ZrO(2) would degrade the densification of the varistor ceramics but inhibit the growth of SnO(2) grains. In the designed range, varistors with 1.0 mol% ZrO(2) presented the maximum nonlinear exponent of 15.9 and lowest leakage current of 110 μA/cm(2), but the varistor voltage increased monotonously with the doping amount of ZrO(2).