Carbon combustion synthesis of Janus-like particles of magnetoelectric cobalt ferrite and barium titanate

Carbon combustion synthesis of oxides was applied for quick and energy efficient production of multiferroic composite of cobalt ferrite and barium titanate to form Janus-like particles matrix structure. The exothermic oxidation of carbon nanoparticles with an average size of 5 nm and a specific surface area of 110 m²/g generates a self-propagating thermal wave with peak temperature of up to 1000 °C. The thermal front rapidly propagates through the mixture of solid reactants (magnetic- CoFe₂O₄ and ferroelectric-BaTiO₃) and results in localized hot-spot sintering of magneto-electric phases to form a nanocomposite structure. Carbon is not incorporated in the product and is emitted as a gaseous CO₂. Existence of discrete CoFe₂O₄ and BaTiO₃phases in the composites nanostructures was confirmed using X-ray powder diffraction along with SEM and TEM analysis. We estimated the activation energy for the combustion synthesis of Janus-like particles to be 112 ± 3.3 kJ/mol, indicating that the barium titanate and cobalt ferrite presence decrease the activation energy barrier of carbon oxidation and facilitate the ignition process of the combustion synthesis. We observe that the as-synthesized samples show magnetoelectric coupling on multiferroic cobalt ferrite–barium titanate ceramic composites.