Mössbauer studies on thermal decomposition of some alkali tris (malonato) ferrate (III) tetrahydrates

Abstract

Thermal decomposition of some alkali tris (malonato) ferrate (III) tetrahydrates, i. e. M3 [Fe(CH2C2O4)3]·4H2O (M=Na, K) has been studied in the temperature range of 433–973 K in static air atmosphere using Mossbauer, IR and TG-DTG-DTA techniques. Mossbauer spectra are reported at different stages to study the mechanism of decomposition. The anhydrous complex decomposed into α-Fe2O3 of varying particle sizes and alkali metal malonate/carbonate in successive stages. In the final stage of remixing of cations, a solid state reaction between α-Fe2O3 and alkali metal carbonate/oxide gives fine particles of the respective ferrites at temperatures lower than for oxalate precursor or even for ceramic method. Thermal stability obeys the order: sodium > potassium > lithium tris(malonato) ferrate (III).