MECHANOCHEMICAL SYNTHESIS OF NIFE2O4 FERRITE

A mixture of crystalline NiO and alpha-Fe2O3 powders in equimolar ratio 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 magnetization measurements, The spinel phase was first observed after 10 h of milling and its formation was completed after 35 h of milling. The synthesized NiFe2O4 ferrite has a nanocrystalline structure with a crystallite size of about 6 nm. Powders obtained after 20, 35 and 50 h of milling, 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.