Influence of the starting powders on the synthesis of nickel ferrite by F. Kenfack and H. Langbein

Crystal Research and Technology

Cryst. Res. Technol. 41, 748 (2006) - Abstract -

Influence of the starting powders on the synthesis of nickel ferrite

F. Kenfack and H. Langbein

Institute of Inorganic Chemistry, Dresden University of Technology, 01062 Dresden, Germany

Keywords	nickel ferrite, taenite, freeze-drying, formate precursor, thermal analysis, mass spectroscopy
PACS	61.10.Nz, 61.66.Fn, 61.66.Dk, 64.60.My, 75.50.Gg
DOI	10.1002/crat.200510663

The thermal decomposition of freeze-dried nickel(II)-iron(III) formate was investigated by means of DTA, TG, mass spectrometry and X-ray powder diffractometry. For the preparation of homogeneous freeze-dried nickel(II)-iron(III) formate precursors, a rigorous control of nickel ion concentration in the precursor solution was required. The decomposition of the reactive nickel(II)-iron(III) formate does not only reflect aspects of single formates, but also an interaction between components which lowers the decomposition temperature. Crystalline nickel ferrite powders were obtained at 600-800°C. This temperature is quite lower than 1100°C employed for the ceramic method. In the presence of air, the regeneration of nickel ferrite from the taenite phase (γNi,Fe) is accomplished at 800°C. This temperature is also 300°C below the temperature employed when the mixtures NiO:α-Fe₂O₃ or Ni:2Fe are the starting powders. The main reason for the high reactivity of the freeze-dried formates and the taenite alloy is the large homogeneity of these precursors.

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