MECHANOCHEMICAL SYNTHESIS OF NIFE2O4 FERRITE

A mixture of crystalline NiO and alpha-Fe2O3 powders in equimolar rati o was mechanochemically treated in a planetary ball mill up to 50 h of milling. The mechanochemical reaction leading to the formation of the NiFe2O4 spinel phase was followed by X-ray diffraction and magnetizat ion measurements, The spinel phase was first observed after 10 h of mi lling and its formation was completed after 35 h of milling. The synth esized NiFe2O4 ferrite has a nanocrystalline structure with a crystall ite size of about 6 nm. Powders obtained after 20, 35 and 50 h of mill ing, as well as the starting mixture without mechanochemical treatment were compacted by cold pressing and sintering. The specific electric resistivity of the compacts greatly depends on the milling time of the powder and decreases by four orders of magliitude as the milling time increases from 0 to 50 h.