Reaction kinetic studies of strontium hexaferrite nanoparticles synthesized by co-precipitation method

Abstract

Nano crystalline strontium hexaferrite, SrFe₁₂O₁₉ powders have been synthesized using co-precipitation method. The ferrite precursors were obtained from aqueous mixtures of strontium chloride and ferric chloride by precipitating strontium 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 formations of nonporous ultrafine particles have been confirmed. About 5 to 10% of the needle like crystals in the ‘as synthesized, condition were transformed to pyramidal structure and most of the crystals are found to have plate like hexagonal structures with increase in heat treatment temperatures. Activation energies and Avrami index ‘n’ were obtained using Johnson-Mehl-Avrami (JMA) equation. The reaction in the temperature range of 800 to 1200°C, proceeds as, instantaneous nucleation and three dimensional growth with activation energy of 168.33 kJ/mole.