Structural and Mössbauer investigation on barium titanate–cobalt ferrite composites

Perovskite and spinels oxides have received renewed attention due to the possibility of combining both structures in di-phase composites to obtain multifunctional materials. In this work, barium titanate (perovskite)-cobalt ferrite (spinel) composite powders with different microstructures were obtained from thermal treatment of amorphous precursors at 500–1100 °C. The precursors were prepared by combining coprecipitation and sol–gel routes. Lyophilization of ferrite prior to mixing was used as a strategy to control interphase reaction. Mössbauer spectroscopy showed that the dispersion of coprecipitated ferrite in a viscous BaTiO3 precursor gel resulted in superparamagnetic behavior and reduction of the local magnetic field of site [B].

► Barium titanate–cobalt ferrite composites were prepared by sol–gel and mixture.
► The microstructure of the sol–gel composite was improved.
► Lyophilization was successful in controlling interphase reaction.
► The hyperfine interactions were strongly affected in the sol–gel composite.
► The dispersion of ferrite in the gel hindered particle growth.