SYNTHESIS OF ZNO-BASED VARISTOR PRECURSOR POWDERS BY MEANS OF THE REACTION SPRAY PROCESS

High-purity, fine-grained oxide ceramic powders that are commonly used for ZnO-based varistors were synthesized by means of the reaction spr ay process. Processing steps included formation of the solutions of zi nc nitrate and/or certain metal additives and spraying of the solution into a heated reaction column using a two-phase nozzle. After water e vaporation from the droplets, the precursor salts were decomposed at e levated temperatures (up to 1473 K) in order to obtain homogeneous oxi de powders with complex compositions corresponding to the final multic omponent varistor system. The decomposition behaviour of the precursor s, as well as the characteristics of the resulting powders: crystallin ity, phase composition, particle shape, morphology and particle-size d istribution, were examined. It was shown that the characteristics of t he reaction spray-derived powders can be controlled by adjusting the s ystem and the solutions parameters.