Synthesis and characterisation of cobaltite and ferrite spinels using thermogravimetric analysis and X-ray crystallography

Abstract

The synthesis for a series of ferrite (MIIFe2O4) and cobaltite (MIICo2O4) spinels was investigated where MII is Mg, Co, Ni, Cu or Zn. The ferrites were prepared at a calcination temperature of 800 °C; the cobaltites at 500 °C. TG–MS indicated that reduction of CoIII to CoII occurs at ca. 800 °C, hence, the lower calcination temperature. For both the ferrites and the cobaltites, the evolution of water and CO2 during the calcination suggests the presence of both species in the precipitates. The observed mass losses indicated that the precursor basic carbonate precipitates for the cobaltite synthesis were predominantly carbonate, while the precursor basic carbonate precipitates for ferrite synthesis were predominantly hydroxide in character. XRD data showed successful synthesis of the ferrites with minimal contamination from the parent oxides, while the cobaltites were observed to be predominantly of the spinel structure.