Preparation of cobalt ferrite from the thermolysis of cobalt tris(malonato)ferrate(III)trihydrate precursor

Abstract

Thermal decomposition of cobalt tris(malonato)ferrate(III)trihydrate precursor, Co 3[Fe(CH 2C 2O 4) 3]·3H 2O has been investigated from ambient temperature to 600 °C in static air atmosphere using various physico-chemical techniques, i.e. TG–DTG–DSC, XRD, Mössbauer and IR spectroscopic techniques. The precursor undergoes dehydration and decomposition simultaneously to yield cobalt malonate and iron(II) malonate intermediates at 205 °C. At higher temperature (325 °C) these intermediate species undergo exothermic decomposition to yield CoO and α-Fe 2O 3, respectively. Finally cobalt ferrite, CoFe 2O 4, has been obtained as a result of solid–solid reaction between Fe 2O 3 and CoO at a temperature (380 °C) much lower than that of ceramic method. SEM analysis of the final thermolysis product reveals the formation of monodisperse cobalt ferrite nano-particles with an average particle size of 45 nm. Magnetic studies show that these particles have a saturation magnetization of 3095 G and Curie temperature of 504 °C. Lower magnitude of these parameters as compared to the bulk values is attributed to the smaller particle size.