Mössbauer Study of the Thermal Decomposition Products of K2FeO4

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Abstract
The thermal decomposition process of a hexavalent iron compound, K2FeO4, was studied by means of the Mössbauer effect. The compound began to decompose in air at about 170°C, and an amorphous product was obtained by the decomposition below 200°C. The product showed a paramagnetic Mössbauer spectrum at 293°K, with an isomer shift and quadrupole splitting of +0.40±0.02 mm/sec and 0.64±0.02 mm/sec respectively; it also showed a magnetically-split six-line spectrum at 4.2°K, with an internal magnetic field of 480±5 kOe. These Mössbauer parameters are characteristic of the Fe3+ state. The intermediate valence states, Fe5+ or Fe4+, were not observed during the decomposition process, and so it was concluded that the Fe6+ ions in K2FeO4 were reduced directly to Fe3+ ions. KFeO2 was formed in air above 250°C, and the temperature dependence of the internal magnetic field showed the Néel temperature of KFeO2 to be very high, 983±10°K.

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