The synthesis and characterization of nickel and cobalt ferrite nanopowders obtained by different methods

Abstract

The ferrite materials, especially of nickel and cobalt, are popular due to their unique mechanical and magnetic properties. The single phase NiFe₂O₄ and CoFe₂O₄ ferrites were synthesized by three methods: the high frequency plasma chemical synthesis, the sol-gel self-combustion, and the co-precipitation technology combined with the hydrothermal synthesis method. Magnetic properties, crystallite size, the specific surface area of synthesized products are characterized. Nanopowders synthesized in the high frequency plasma have a specific surface area in the range of 28–30 m²/g (the average particle size 38–40 nm, crystallite size ~40 nm), but a wider particle size distribution is in the range of 10–100 nm with some particles of 200 nm. The ferrite nanopowders obtained by the sol-gel self-combustion and hydrothermal synthesis method have the specific surface area of 40 ± 3 and 60 ± 5 m²/g (average particle size 25–30 nm and 19–26 nm, crystallite size 10–20 nm and 12–20 nm), respectively. Cobalt ferrites after synthesis are characterized by the saturation magnetization M_S of 75 emu/g (for plasma chemical synthesis), 53 emu/g (for the self-combustion method), and 57 emu/g (hydrothermal synthesis). The saturation magnetization for nickel ferrites is 44, 29 and 30 emu/g, respectively. After the thermal treatment up to 900 ºC the particle size of all ferrites increases, but their magnetic properties are approaching those of monolithic ferrites.

DOI: http://dx.doi.org/10.5755/j01.ct.67.1.15824