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Reaction mechanism of strontium cobaltite synthesis from equimolar mixture of Sr(NO3)2 and Co(NO3)2∙6H2O under air atmosphere

Aslan, Cemal, Ilhan, Sedat, Kalpakli, Ahmet Orkun, Kahruman, Cem, Yusufoglu, Ibrahim
Thermochimica acta 2019 v.676 pp. 52-63
Fourier transform infrared spectroscopy, X-ray diffraction, air, ambient temperature, carbonation, cobalt, cobalt oxide, cooling, heat, nitrates, oxygen, reaction mechanisms, stoichiometry, strontium, thermal analysis, titration
Strontium cobaltite was produced by heating the mixture containing equimolar amounts of Sr(NO3)2 and Co(NO3)2∙6H2O under dynamic air atmosphere. The reactions occurred during heating were determined and the intermediate and final products obtained at each reaction step were characterized using TG/DTA-MS, ICP-OES, XRD and FT-IR techniques. The oxygen stoichiometry of strontium cobaltite was determined using iodometric titration method and carbonation process.It was determined by thermal analysis results that Co(NO3)2∙6H2O was decomposed to CoO by forming the intermediate products Co(NO3)2∙4H2O, Co(NO3)2∙2H2O, Co(NO3)2∙H2O, Co(NO3)2, CoOOH, Co2O3 and Co3O4. Sr(NO3)2 was decomposed to SrO. Sr6Co5O15 was formed by solid state reaction of SrO, Co3O4 and O2. Sr2Co2O5 was produced at elevated temperatures from Sr6Co5O15 and Co3O4.Analyses carried out for the characterization of compounds obtained at different isothermal conditions showed that final product Sr2Co2O5 was obtained via Sr14Co11O33 and Sr6Co5O15. Sr2Co2O5 was decomposed to a mixture of Sr6Co5O15 and Co3O4 with a mole ratio of 1 : 0.333 during slow cooling to the room temperature.