Mise en évidence de CaF 2e 4O 6 et détermination des structures cristallines des ferrites de calcium CaFe 2+ nO 4+ n( n = 1, 2, 3): nouvel exemple d'intercroissance
The synthesis of a new calcium ferrite CaFe 4O 6 has been carried out at 1125°C under a controlled atmosphere of H 2H 2O. The existence of this compound modifies a part of the diagram FeCaO. The crystal structures of the ferrites CaFe 2+ nO 4+ n ( n = 1, 2, 3) have been resolved on a series of single crystals; these ferrites crystallize in the orthorhombic system, space group Cmcm, with the average parameters a = 3.04 Å, b = 10 Å, c = 10 + 2.65 nÅ. The three structures derive from each other through an intergrowth process, in the direction of the c axis, with CaFe 2O 4 blocks between the FeO blocks. The coordination of the iron atoms is slightly changed by the nature of the neighboring blocks during stacking.