REACTION SINTERING OF ZINC FERRITE DURING CONSTANT RATES OF HEATING

The reaction sintering of equimolar quantities of zinc oxide and ferric 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 ferrite powder. For the heating rate of 1-degrees-C/min, the densifications of the reaction-sintered sample and the calcined sample were approximately the same. However, as the heating rate increased, the density at any temperature increased slightly for the reaction-sintered sample but 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 densification. Relative densities of >95% were obtained for both the reaction-sintered sample and the calcined sample under identical sintering conditions (1-10-degrees-C/min to 1350-degrees-C). Reaction sintering in a steep temperature gradient produced a nearly fully dense body prior to complete reaction; a composite microstructure consisting of fine zinc oxide grains in a matrix of zinc ferrite was obtained.