Study On The Preparation And Magneto-optical Properties Of Layered Perovskite Nanomaterials

Photocatalysis has the ability to use solar energy to drive reactions at room temperature directly.It is an ideal technology to solve environmental pollution and produce clean energy.At present,the researches of semiconductor photocatalyst based on TiO2 have encountered bottleneck.Therefore,new photocatalytic materials need to be found in order to improve the utilization of solar energy,enhance the photocatalytic efficiency,save energy and reduce secondary pollution.In recent years,Bismuth-based Aurivillius oxides with a general formula Bi4Bin-3Fen-3Ti3O3n+3(n denotes the number of perovskite-like layers)have attracted considerable attention due to their ferroelectric and magnetic properties.The coexistence of ferroelectricity and ferromagnetism at room temperature can be obtained by doping or changing the number of layers of materials.Recently,more and more studies have been carried out on the photocatalytic properties of layered oxides due to their suitable band gap.Researches show that the built-in electric field based on spontaneous polization inside the ferroelectric materials is favorable for the separation of the photogenerated electron-hole pair,and the ferromagnetism is beneficial to magnetic recovery.Therefore,these oxides have potential applications in photocatalysis.In this paper,the effects of magnetic elements and rare earth elements on the morphology,magnetism and photocatalytic efficiency of four(n=4)and five(n=5)layered perovskite nanomaterials have been studied.The relationship between morphology and physical properties was also explored by adjusting the alkaline concentration to change the size and morphology of the materials.This thesis is divided into six chapters as follows:Chapter 1:We briefly described the structure,the research progress and modification techniques of layered perovskite nanomaterials.The photocatalytic properties and their basic principle of photocatalytic materials were explained,and the ferromagnetism and ferroelectricity were introduced.The main contents of this paper are summarized.Chapter 2:The related chemical reagents,instruments and equipment in this paper were introduced.As well as the preparation methods,the property characterization and the test analysis method of the materials were also introduced.Chapter 3:Samples prepared with different heat treatment time were synthetised by hydrothermal method.It was found that the optimum preparation conditions of four layered perovskite Bi5FeTi3O15(BFTO,n=4)samples were 200? and 72 h.Under this condition,Ni-doped BFTO(Bi5Fe1-xNixTi3O15:BFNTO-x,x=0,0.05,0.1,0.15,0.2)samples were prepared.The morphology and structure of the samples were characterized.And the magnetic and photocatalytic performances of the samples were measured.It was found that the magnetic performances of BFNTO-x are significantly ameliorated after Ni doping.Chapter 4:Firstly,Bi5-yEuyFeTi3O15(BEFTO-y,y=0,0.05,0.1,0.15,0.2)samples were prepared hydrothermal method.It was found that doping improved the morphology and photocatalytic performances of the samples.Then Bi5-yEuy Fe0.9Ni0.1Ti3O15(BEFNTO-y,y=0,0.1,0.3,0.5)were prepared by doping Eu at A-site.The results show that the doping of Eu has a significant effect on the photocatalytic properties and magnetic properties.The sample Bi4.9Eu0.1Fe0.9Ni0.1Ti3O15 showed superior photocatalytic and magnetic properties.Meanwhile,the Bi4,9Eu0.1Fe0.9Ni0.1Ti3O15 sample can be magnetically recovered at room temperature to avoid secondary pollution of water.Chapter 5:Firstly,we studied the morphology,photocatalysis and magnetism of Co-doped five-layered perovskite Bi6Fe2Ti3O18(Bi6Fe2-xCoxTi3O18:BFCTO-x,x=0,0.2,0.4,0.6,0.8,1).Then the influences of diverse alkaline concentration on the size and morphology of the samples were explored by adjusting the concentration of NaOH.And the connection between morphology and physical performances was studied.The results show that with the increase of NaOH concentration,the size of the sample increase,the specific surface area decreases,the saturation magnetization(2Ms)increases,and the photocatalytic efficiency becomes worse and worse.Chapter 6:Researches on the layered perovskite nanomaterials is summarized,and the direction of future work is point out.