Solid state synthesis of Ca(2)Fe(2)O(5 )by reactive firing of calcite and siderite


The brownmillerite phase Ca2Fe2O5 was processed by the reactive firing of calcite and a natural siderite for prospective catalytic applications. Thermogravimetry and X-ray diffraction (XRD) was used to monitor the decomposition of precursors and its dependence on heating rate and atmosphere. Taguchi planning was used to assess the impact of firing temperature, time, and rate of heating on the conversion of precursors reflected by I(121)sp : I(121)b peak intensity ratio of main XRD reflections of secondary spinel phase CaFe2O4 and brownmillerite. The onset of additional minor phases (Ca2Al2SiO7 and Ca2SiO4) was ascribed to the reaction of a fraction of calcia with gangue components of the siderite precursor. Thermodynamic modelling was used as a guideline for syn-thesis in non-oxidising conditions to hinder the onset of CaFe2O4. These guidelines allowed one to obtain high conversion to Ca2Fe2O5 with enhanced crystallinity at 700 degrees C, in an inert Ar atmosphere. Faster reactivity at T >= 800 degrees C in this oxygen-lean atmosphere, leads to highly crystalline Ca2Fe2O5 coexisting with the onset of wustite and/or metallic Fe, which account for the oxygen balance, and calcium silicates, by reaction of calcia with silica.




Materials Science


Antunes, I; Ruivo, LCM; Tarelho, LAC; Yaremchenko, AA; Frade, JR

nossos autores


This work was developed withing the scope of the projects NOTARGAS (ref. POCI-01-0145-FEDER-030661), CICECO -Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020 and CESAM -Centre for Environmental and Marine Studies, UIDB/50017/2020, UIDP/50017/2020, LA/P/0094/2020, financed by national funds through the FCT/MEC (PIDDAC). L. Ruivo acknowledges to the Portuguese Foundation for Science and Technology for the PhD scholarship grant (ref. SFRH/BD/129901/2017). The authors would also like to thank Aleksandr Bamburov for the experimental assistance, and the SIDCO Minerals Inc. Company for providing the siderite.

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