Investigation of the formation of nickel-zinc ferrite from coprecipitated oxalates

Abstract

Homogeneous solid-solution oxalates of Ni 2+, Fe 2+ and Zn 2+ ions were synthesized by coprecipitation from acetate solutions using a special double-inlet technique and freeze drying of the precipitates. The mixed oxalates decomposed on heating to form ferrites with a spinel structure. The conditions of precipitation, the characteristics of the precipitates and the decomposition conditions affect phase formation and product characteristics. When preparing the oxalate precursor by dropwise addition of ammonium oxalate solution to a metal sulphate solution, as well as the ferrite, simple oxides are partially formed on decomposition. On decomposition of the substances prepared according to the method described here, however, the appropriate ferrite was formed as the sole phase. The grain size distribution of the oxalate precursors can be widely influenced by the precipitation conditions. For finely dispersed initial powders, the grain size distribution and grain shape are extensively maintained during the decomposition process.