Heat-induced charge transfer in cobalt iron cyanide

The heating of Co(2+) ferricyanide above 80 degrees C induces an inner charge transfer from Co(2+) towards Fe(III) to form the mixed valence system Co(2+)Co(III) ferri- ferro-cyanide. This charge transfer takes place preserving the material framework and forming a solid solution of the initial and final species. The cell edge of the cubic cell (Fm-3m) of this solid solution follows a regular variation with the material composition. This mixed valence system was characterized using X-ray diffraction, infrared, thermo-gravimetric, Mossbauer and magnetic measurements. Its formation is easily detected by the appearance of an intermediate v(CN) absorption band in the infrared spectra at around 2120cm(-1), 40cm(-1) below and above the observed frequency for this vibration in Co(2+) ferri- and ferro-cyanide, respectively. (c) 2006 Elsevier Ltd. All rights reserved.67112289229