Study On The Properties Of Fe-Ni/Co Aurivillius Multiferroic Material And Effect Of A-site Sm Doping

The mismatch of A-site or B-site ions in the bismuth layered perovskite causes the metal ions to deviate from the center of the oxygen octahedron or the oxygen octahedron is distorted and tilted,causing the spatial symmetry and time symmetry to be broken,thus showing ferroelectricity and ferromagnetic.In this dissertation,starting from 4-layer and 5-layer Aurivillius multiferroic material,to study the origin of magnetic of Aurivillius multiferroic materials through the B-site Ni/Co doping and A-Site Sm doping.Impact mechanism.This graduation thesis is mainly divided into six chapters:The first chapter introduced the development history and application of multiferroic materials.Discusses the essential origin of multiferroic from the concepts and mechanisms of ferromagnetic materials and ferroelectric materials.The multi-iron simple perovskite extends to complex multi-layer perovskite,and then focuses on the bismuth-based layered perovskite multi-ferrous material,and discusses its research status and modification methods.Some ideas are presented according to the research actualityThe second chapter introduced the basic processing technology and principles.And introduces the testing methods and principles from microstructure and properties of materials.The third chapter introduces the effect of Ni element doped BisFeTi3O15 on the morphology and properties of multiferrous materials.We found that the polyferrite prepared by the hydrothermal method is relatively pure.Ni substitution can significantly enhance the ferro.The maximum magnetic property(2Ms=1.28emu/g)was achieved at a doping amount of 0.2,which was twice as high as that of BFNT-0.2 prepared by solid-phase method(2Ms=0.53emu/g).In the fourth chapter,the effect of doping Bi with different content of Sm element on Bi6Fe1.4Ni0.6Ti3O18 ceramic material was studied.Sm substitution is found to cause a transition from an orthorhombic phase to a tetragonal phase at BSFNT-0.30 samples,and again to an orthorhombic phase at higher Sm content.The 2Pr reaches a maximum value of 15.4 ?C/cm2 when the Sm content is 0.30.The enhancement of ferroelectric of BSFNT-x are attributed to the structural distortion and oxygen vacancies caused by Sm substitution The room-temperature remanent magnetization(2Mr)reached a maximal value was 1.9 emu/g in the BSFNT-0.25 samples.Dielectric loss exhibits the characteristics of dielectric relaxation from 120 K to 500 K,which can be ascribed to hopping of electrons between Fe3+ and Fe2+ ions.XPS result indicates that a small amount of Sm modification enhances the inhibition of oxygen vacancies.Also,the content of Fe2+ increases when the introduced Sm is more than 0.20.The fifth chapter mainly studies the properties and mechanisms of the randomly-oriented(BFCT-1)and(00 10)oriented(BFCT-2)Multiferroic thin films of Bi5Fe0.5Co0.5Ti3O15.At RT,The 2Pr of BFCT-1 and BFCT-2 films are measured to be 55.4?C/cm2 and 34.8?C/cm2,respectively.The BFCT-2 film demon strates the stronger magnetization with a saturation magnetization(2Ms)of 1.05 emu/cm3,and the BFCT-1 film also shows a well ferromagnetic behavior with smaller 2Ms was about 0.56 emu/cm3.The shape of the hysteresis loop of the BFCT-2 film has almost no change after fatigue measurement,and has strong fatigue resistance.The sixth chapter is a summary of the text and outlook for future.