Heat induced charge transfer in cobalt iron cyanide.

RICARDO MARTÍNEZ GARCÍA; M. KNOBEL; G. GOYA; M. C. GIMENEZ; F. M. ROMERO; E. REGUERA RUIZ

JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2006 vol. 67 p. 2289 - 2299

0022-3697

The heating of Co(2+) ferricyanide above 80 ºC 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, Mo¨ ssbauer and magnetic measurements. Its formation is easily detected by the appearance of an intermediate n(CN) absorption band in the infrared spectra at around 2120 cm-1, 40cm-1 below and above the observed frequency for this vibration in Co(2+) ferri- and ferro-cyanide, respectively.