Synthesis And Properties Studies Of Multiferroic BiFeO₃ And Related Composite Materials

BiFeO₃ as a new type of perovskite-type multiferroics has great advantage applications in magnetic sensors,detectors,information storage and other aspects.However,the weakness of magnetization,leakage current,and magnetoelectric coupling is adverse to its practical value.In this paper,the effects of doping and annealing treatment and compositions on the lattice,electric and magnetic properties of BiFeO₃ materials and composites were investigated.Firstly,the Co-doped multiferroics material BiFe_1-xCo_xO₃?x=0,0.05,0.1?series ceramic samples were prepared by sol-gel method.The crystal structure,ferroelectricity,Leakage current,magnetic and other aspects of the effect were discussed about the sample after 600? annealing,which its physical performance was changed.The results of the XRD patterns of BiFe_1-xCo_xO₃?x =0,0.05,0.1?series show that the samples belong to the distorted perovskite structure and the space group is R3c?161?.Co doping is beneficial to suppress the growth of the second phase,but the annealing treatment can not only increase the growth of the main phase but also that of the second phase.From the current density-electric field?J-E?curve,the leakage current density is increased with Co doping,while annealing treatment leads it decrease.For the undoped sample,the leakage current density was improved after annealing.From the electric hysteresis?P-E?curve,it can be concluded that the remnant polarization for the Co-doped sample was improved before annealing while the samples annealed do the opposite effect.However,the remnant polarization of pure BiFeO₃ annealed is obviously enhanced,and its ferroelectric properties are improved.From the hysteresis loop?M-H?shows that Co-doped samples of the ferromagnetism was significantly enhanced after annealing.Secondly,the magnetite La_0.7Ca_0.3MnO₃ with perovskite structure has good ferromagnetism,and it is beneficial to obtain the multiferrous composite material by combining it with the synthesized single-phase BiFe_0.95Co_0.05O₃ sample.In this paper,?1-x?LCMO:?x?BFCO?x = 0,0.1,0.2,0.3,0.4,0.5,0.6,0.8,1.0?complex was obtained by solid solution method.The results show that the BiFe_0.95Co_0.05O₃ phase of the composites is almost incompatible with the La_0.7Ca_0.3MnO₃ phase from the XRD pattern,and the SEM image indicates the chemical phase separation.However,the lattice constant of x = 0.6 samples is very large,indicating the interaction between the lattice of two-phases.After analysis of the magnetic,the composites produced weak ferromagnetic properties with the introduction of BiFe_0.95Co_0.05O₃,and the composites exhibited coexistence of ferromagnetism and paramagnetism at room temperature.