Modified Citrate Gel Techniques to Produce ZnO-Based Varistors (Part II—Electrical Characterisation)

The electrical characteristics of doped ZnO pellets prepared by novel, modified citrate gel routes and the conventional mixed oxide route were compared. The mixed oxide route produced rather inhomogeneous materials at the sintering temperatures employed in this study (970 °C and 1000 °C). In contrast, the modified citrate gel routes enabled some control over the location of the minority components incorporated into the ZnO. By positioning these components according to their function, varistor pellets with higher nonlinearity coefficients, higher characteristic voltages and slightly higher energy absorption abilities than those of the conventional mixed-oxide route were prepared. Differences in the electrical characteristics of varistors prepared by different routes but with apparently similar microstructures was taken to indicate successful control over the compositional homogeneity.