REACTION SINTERING OF ZINC FERRITE DURING CONSTANT RATES OF HEATING

The reaction sintering of equimolar quantities of zinc oxide and ferri c oxide was investigated under conditions of constant rates of heating (1-10-degrees-C/min from room temperature to 1350-degrees-C) and the data were compared with those for a calcined, single-phase zinc ferrit e powder. For the heating rate of 1-degrees-C/min, the densifications of the reaction-sintered sample and the calcined sample were approxima tely the same. However, as the heating rate increased, the density at any temperature increased slightly for the reaction-sintered sample bu t decreased slightly for the calcined powder. The factors responsible for this slight difference in sintering between the reaction-sintered sample and the calcined sample are discussed. For the constant heating rates used, the reaction was completed prior to any significant densi fication. Relative densities of >95% were obtained for both the reacti on-sintered sample and the calcined sample under identical sintering c onditions (1-10-degrees-C/min to 1350-degrees-C). Reaction sintering i n a steep temperature gradient produced a nearly fully dense body prio r to complete reaction; a composite microstructure consisting of fine zinc oxide grains in a matrix of zinc ferrite was obtained.