Fourier transform far-infrared spectroscopic evidence for the formation of a nickel ferrite precursor in binary Ni(II)-Fe(III) hydroxides on coprecipitation

Fourier transform infrared (FTIR) spectroscopic measurements, performed in the far-IR region (200-800 cm(-1)) on binary coprecipitated Ni(II)-Fe(III) hydroxides (20-60 at.% Fe/(Ni + Fe)), are presented and discussed. Heating the sample containing 60 at.% Fe to 600 degrees C, monitored by differential scanning calorimetry (DSC) measurements, results in the formation of a nickel ferrite structure from its precursor present in binary hydroxides. The role of Fe-to-Ni ratio non-uniformities within the surface and bulk of the binary hydroxide crystallites, as revealed by Mossbauer measurements, Auger electron spectroscopy and depth profiling performed previously, is also discussed with regard to the formation of alpha-Fe2O3 and NiO impurities on thermal treatment.