Moessbauer study of a state of iron atoms during low-temperature cristobalite synthesis in the SiO2-Fe2O3 system

Moessbauer investigation into the process of low-temperature crystallization of cristobalite from SiO2 + 0.3 mass% of 57 Fe2O3 composition gel under hydrothermal conditions, are conducted. It is shown that in the source gel the paramagnetic Fe3+ ions are present in the form of a diluted impurity in a diamagnetic matrix, and a spin-lattice relaxation of their magnetic moments is observed therewith. In the course of synthesis reduction of a part of iron atoms up to two-valent high-spin state rakes place under sixfold oxygen coordination, and then with cristobalite appearance the back oxidation and production of magneto-ordered Fe2O3 particles with 80 A < d < 300 A dimensions take place