Synthesis of SrFe(Al)O3−δ–SrAl2O4 nanocomposites via green route

A ceramic nanocomposite of SrFe(Al)O3−δ and Sr3Al2O6 was obtained using the controlled combustion of a previously synthesized chitosan-Sr-Fe-Al precursor. The complex formed by chitosan and metal ions in the organometallic precursor was confirmed by FTIR, TGA and DSC analysis. The nanocomposite consisted of hard agglomerates containing nanoparticles of Sr-Fe-Al oxides with oval morphology and an average diameter ≤ 9 nm. The DRX analysis indicated a composition of SrFe(Al)O3−δ and Sr3Al2O6 phases. Also, HRTEM and XPS verified the formation of a principal phase of ceramic composite identified as SrFeO3–x(2.5 ≤ x ≤ 3.0) possibly of aluminum-substituted structure, and minority phases of SrAl12O19 and SrAl2O4. Furthermore, a by-product of strontium carbonate was found as traces on the composite oxide surface. It was attributed to solid-gas reactions of strontium oxide with carbon dioxide, the latter produced during the oxidative decomposition of the biotemplate. Also, moderated calcination temperature limits the total decomposition of SrCO3.