Surface Engineering Lab, Metallurgical and Materials Engineering Department, Indian Institute of Technology Roorkee, IITR, Roorkee-247667, Haridwar, Uttarakhand, India.
Nano crystalline barium hexaferrite, BaFe12O19 powders have been synthesized using co-precipitation method. The ferrite precursors were obtained from aqueous mixtures of barium chloride and ferric chloride by precipitating barium and iron using 7.5 M sodium hydroxide solution. These precursors were heat treated at 800 and 1200°C in nitrogen atmosphere. The decomposition behaviour and reaction kinetics were investigated by means of DSC/DTG/TG for three heating rates. The various phases associated therein were identified by X-ray diffraction (XRD). From field emission scanning electron microscopy (FESEM) study, the formation of nonporous ultrafine particles have been confirmed. About 10 to 20% of the needles like crystals in the ‘as synthesized’ condition were transformed to pyramidal structure with increase in heat treatment temperatures. Activation energies and Avrami index ‘n’ were obtained using Johnson-Mehl-Avrami (JMA) equation. Reaction in the temperature range of 800–1200°C, proceeds as, instantaneous nucleation and three dimensional growth with activation energy of 178.15 KJ/mole.
