EFFECT OF CALCINATION ON STRUCTURAL AND MAGNETIC PROPERTIES OF CoFe2O4 SYNTHESIZED VIA CO-PRECIPITATION METHOD

Abstract

Various nanoparticles have been dispersed in carrier fluid to form functional nanofluids that may work on its own or by applying external stimulating field. Magnetically stimulated nanofluid will be influenced by the magnetic properties of the nanoparticles i.e. saturation magnetization that determine the effectiveness of magnetic domain arrangement. Magnetite has been widely studied as an excellent magnetic material for various field applications. Despite having excellent magnetic properties, it is highly susceptible to oxidation and poses limitation to various applications. Therefore, substitution of cobalt in the magnetite lattice is one of the solutions and has shown a remarkable increase in the magnetic and structural properties of cobalt ferrite, CoFe₂O₄. It possesses high chemical stability and excellent magnetic properties that is suitable to be dispersed in fluid for magnetic fluid synthesis. CoFe₂O₄ nanoparticles were synthesized via co-precipitation method and its properties were compared with Fe3O4 to study the effect of Co²⁺ cation substitution on the enhancement of structural and magnetic properties of cobalt ferrite. Magnetic properties e.g. saturation magnetization and coercivity were measured using VSM. Irregular shape of particles was observed for all three samples, with crystallite sizes vary from 37.41 to 50.46 nm, calculated at (311) plane. FTIR analysis confirms the formation of ferrite structure by locating the characteristic peak of tetrahedral metal-oxygen bonding around 580 cm-1 in both Fe₃O₄ and CoFe₂O₄. However, the peak could not be identified in the as-precipitated CoFe₂O₄ sample, due to the unwanted impurities e.g. Na and Cl ions which the presence was confirmed by EDX analysis. Post calcination at 600 and 800 °C shows remarkable improvement in the saturation magnetization, with highest saturation magnetization of 65.40 emu/g achieve at 800 °C. In conclusion, calcination has improved the structural and magnetic properties of CoFe₂O₄ by impurities removal and also enhances the crystallinity of the particles.