Effect of La2O3-treatment on textural and solid–solid interactions in ferric/cobaltic oxides system

Pure and La2O3-containing (0.75–3.0 mol%) Fe2O3/Co3O4 solids were prepared by thermal treatment of their carbonates at 500–700 °C. The produced solids were characterized using XRD, HRTEM, EDX and nitrogen adsorption at −196 °C. The results revealed that pure solids calcined at 600 and 700 °C consisted of nanosized CoFe2O4 phase, while pure mixed solids calcined at 500 °C consisted of trace amount of CoFe2O4 and unreacted Fe2O3, Co3O4 phases. The presence of 0.75 mol% La2O3 enhanced solid–solid interaction between Fe2O3 and Co3O4 at 500 °C yielding CoFe2O4. The ferrite phase existed also in all mixed oxides upon treated with La2O3 besides LaCoO3 phase. LaCoO3 existed as a major phase in all mixed oxides treated with 3 mol% La2O3. La2O3-treatment modified the crystallite size of all phases present to an extent dependent on calcination temperature and amount of La2O3 content. This treatment decreased effectively the SBET of all mixed solids.

Graphical AbstractTEM photographs of pure mixed oxides calcined at 500 °C.Figure optionsDownload as PowerPoint slideHighlights
► Cobalt ferrite exhibit chemical stability, low electric loss and high coercivity.
► Cobalt ferrite is used in microwave devices, computer memories and magnetic storage.
► Solid–solid interactions in ferric/cobaltic oxides system were investigated.
► La2O3-treatment modified surface compositions of the system investigated.
► All phases present in various solids existed as nanosized solids.