Distorsion cristalline et distribution des cations dans les spinelles de la serie CoMnxFe2−xO4

By using neutron diffraction together with anomalous dispersion X-ray diffraction, it has been possible to ascertain the distribution of close atomic numbered cations in CoMn_xFe_2?xO₄ system spinels.At 950°C, these compounds have a cubic structure in the range 0 ? x ? 1.25 and exhibit a macroscopic tetragonal distortion as soon as 60% of the Mn³⁺ ions occupy octahedral sites.The great mobility of cobalt between both types of sites has been pointed out; it can be related to oxidation and reduction phenomena. In these compounds, Fe³⁺ iron remains neutral towards four or six coordinences.