Bi Multiferroic Materials At Room Temperature

Multiferroic materials are a class of functional materials，which simultaneouslyoffer at least two or more orders of （anti）ferroelectric,（anti）ferromagnetic andferroelastic. Among of these, ferroelectric-（anti）ferromagnetic multiferroic materials（also known as magnetoelectric materials） have recently attracted extensive attention inacademic and engineering fields. Magnetoelectric multiferroic material can generally bedivided into single-phase magnetoelectric materials and composite magnetoelectricmaterial.But most of the single-phase magnetoelectric materials areanti-ferromagnetic material, and the magnetoelectric effect is very weak,and theoperating temperature is very low, so the application prospects is poor at present.In this thesis, room temperature Bi-based single-phase magnetic materials havebeen studied.After analysis of the structural characteristics, the origin of magneticproperties and ferroelectricity, doping mechanism,we study the materials and processinnovatively in order to make them become the single-phase magnetoelectric material ofpractical value. The main contents include:1, Synthesis of the pure phase BFCO ceramics and La doped BLFC ceramic underthe conditions of2～5GPa pressure,800℃～1100℃. Through the measurement ofmagnetic and electric properties of materials, studied the material’s magnetic,ferroelectric properties and the influence of La doped ceramic on th magnetic andelectric properties of materials, The factors affecting its magnetic and electric propertieswere also analysised.2,Study of the influence of Co-doped on the magnetic and electrical properties ofCo-doped Bi₅Fe_1-xCoxTi₃O₁₅.Through the measurement of magnetic properties,electrical properties and microscopic analysis of materials,We obtain the optimal dopingratio was obtained. At the same time, the reason that Co-doping can change themagnetic properties,ferroelectric properties and material microstructure of BFTO wasalso tentatively explained.3,The effect of A-site doped La on the magnetic properties,ferroelectricproperties,microstructure and morphology.At last, the optimal doping ratio was obtained.