Preparation and characteristics of Ni-ferrite powders obtained in the presence of fused salts

Abstract

This paper describes Ni-ferrite formation in the presence of Li2SO4-Na2SO4 molten salts, and in particular the effects of the raw materials, amount of salts, heating temperature and time on the size and shape of the ferrite powders, as well as on the rate of ferrite formation. The molten salts accelerate ferrite formation and complete ferrite formation is attained at lower temperatures than in solid state reactions. Ferrite powders with two types of shapes are obtained from NiO with different particle sizes and aggregation states; one is similar to the starting Fe2O3 particles and the other has an octahedral crystal habit. The difference follows from the different dissolution rates of Fe2O3 and NiO. Growing particles in molten salts have a crystal habit, but the most stable particle shape is rounded.