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 o 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 α-Fe 2 O 3 and NiO impurities on thermal treatment.