Synthesis Of BaTiO₃/CoFe₂O₄ Magnetoelectric Composite Materials By A Chemical Chelation Process

Multiferrous composites consisting of piezoelectric and piezomagnetic component phases show a magnetoelectric coupling effect (ME) due to the magnetically or electrically induced mechanical deformation between two phases. To the magnetic field induced ME effect, the applied magnetic field generates a strain in piezomagnetic phase that deforms piezoelectric phase. As a result, the deformation of piezoelectrical field induced ME effect can be realized by applying an electric field. Similarly the electrical field induced ME effect can be realized by applying an electric field.The ME effect occurs as a product property between piezoelectric and piezomagnetic phases and is not available in their individual component phase. Piezoelectric and piezomagnetic properties of magnetoelectric particulate barium titanate (BaTiO₃) and cobalt ferrite (CoFe₂O₄) composite materials have been intensely investigated in recent years since it has excellent magnetoelectric properties. However, the conventional process of mixing and sintering barium titanate (BaTiO₃) and cobalt ferrite (CoFe₂O₄) powders resulted in poor insulation properties of the composite materials due to the inhomogeneous distribution of cobalt ferrite phase in the barium titanate matrix, which limits the ME properties of the BTO/CFO composites because of the inefficient polarization of BaTiO₃.In this study, barium titanate (BaTiO₃) and cobalt ferrite (CoFe₂O₄) composite materials are prepared by a chemical chelation process. EDTA and citric acid are used as complexation agents. The molar ratios of BaTiO₃ and CoFe₂O₄ are 1:0.1, 1:0.25 and 1:0.5 respectively. The decomposition processes of the precursors are investigated by thermal analysis (DTA/TG/DTG), Fourier infrared (FTIR) and X-ray diffraction (XRD). The phase separation of BaTiO₃ and CoFe₂O₄ is identified by XRD, and the electrical resistivity of the composites was measured.The experimental results indicate that below 200℃the weight loss in the decomposition process is due to water evaporation. The exothermic event between 200℃and 300℃is attributed to the decomposition of NH₄NO₃ by-product. The decomposition of EDTA and citric acid components starts from 300℃and completes at 500℃. At about 400℃, the crystalline BaTiO₃ phase is formed and at about 600℃two phases of BaTiO₃ and CoFe₂O₄ are clearly identified without the existence of...