Combustion synthesized ZnO powders for varistor ceramics

Abstract

Commercial ZnO varistor ceramics are multicomponent, with minor amounts of added oxides that play important roles, both in the strict electrical sense and for the control of the microstructure. The present work describes the straightforward combustion synthesis of pure and doped ZnO powders from stoichiometric mixtures of the relevant water soluble metal nitrates as cation precursors and urea as Fuel. The mixtures were ignited at 500 degrees C resulting in a dry, very fine powder. The as-prepared combustion products, characterized by XRD, SEM, TEM and BET, show high specific surface area, have very small particle sizes and are crystalline, with atomic level homogeneity. Implications on sintering and electrical behaviour are discussed. @ 1999 Elsevier Science Ltd. All rights reserved.