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离子掺杂M型锶铁氧体的制备及第一性原理研究
Preparation and First-principles Study of Ion Doped M-type Strontium Ferrite
【作者】 宋扬;
【导师】 吴泽;
【作者基本信息】 哈尔滨理工大学 , 材料物理与化学, 2020, 硕士
【摘要】 M型锶铁氧体属于永磁材料,由于M型铁氧体的单轴磁晶各向异性和矫顽力较高、化学稳定性好、价格低廉等特点,因此可以应用在航天国防、工业制造以及电子器件等领域。随着工业及国防等领域的迅猛发展,不但对M型锶钡铁氧体的需求量增加,而且对产品的性能要求也越来越严格。所以大量的科研学者不断通过研究它的制备方法、工艺参数、新配方等来提高它的磁性能。近年来利用稀土离子掺杂的方法改善锶铁氧体性能已经成为该领域研究的热点。本研究主要采用溶胶凝胶自燃烧和化学共沉淀两种方法制备了Sm-Ni和Gd-Ni等价取代的M型锶铁氧体。并采用XRD、FTIR、SEM和VSM表征测试方法,分析样品的物相组成、微观形貌和磁性能等。使用Material Studio建模,VASP进行第一性原理计算,经过结构优化计算出稳定的结构,静态自洽后计算它的电子结构特性和磁性能等。实验及计算结果如下:1. 使用化学共沉淀法制备Sr1-x(Sm/Gd)xFe12-xNixO19(x=0,0.05,0.1,0.15,0.2)。Sm-Ni联合取代时:当0≤x<0.2时,样品为单一的六方铁氧体,当x=0.2时开始出现杂质相Fe2O3和Sm Fe O3。晶粒形状近似为六边形,尺寸为80-150 nm。x=0.15时,最大Ms=43 emu/g和最大Mr=27.06 emu/g,在x=0时,最大Hc=6452 Oe,并且随着掺杂量增加而减小。Gd-Ni联合取代时:当0≤x<0.15时,为单一的M型锶铁氧体,当x=0.15时开始出现杂质相Fe2O3和Gd Fe O3。晶粒形状近似为六边形,尺寸为80-150 nm。在x=0.1处,最大Ms=41.04 emu/g,最大Mr=24.73 emu/g,在x=0时,最大Hc=6452 Oe,并且随着掺杂量增加而减小。2. 使用溶胶凝胶自燃烧法制备Sr1-x(Sm/Gd)xFe12-xNixO19(x=0,0.05,0.1,0.15,0.2)。Sm-Ni联合取代时:当0≤x<0.1时,样品为单一的六方铁氧体,当x=0.1时开始出现杂质相Fe2O3。晶粒形状为六角片状和部分不规则形状。尺寸为120-200 nm。在x=0.05时,最大Ms=43.71 emu/g,最大Mr=26.35 emu/g,在x=0时,最大Hc=6620 Oe,并且随着掺杂量增加而减小。Gd-Ni联合取代时:当x=0时为单一的六方铁氧体相,当x=0.05时开始出现杂质相Fe2O3。晶粒形状为六角形片状和部分不规则形状,尺寸为100-300 nm。在x=0.05处,最大Ms=46.26 emu/g,最大Mr=28.74 emu/g,在x=0时,最大Hc=6620 Oe,并且随着掺杂量增加而减小。3. 使用基于DFT的第一性原理计算M型锶铁氧体稳定结构,并使用GGA+U的近似方法优化晶体结构计算性质。算出Sr Fe12O19的带隙为1.681 e V,为本征半导体特性,总磁矩为39.97μB。并计算Sr0.5Sm0.5Fe11.5Ni0.5O19的稳定的晶体结构,和未掺杂相比晶格常数略微减小,带隙值降低至0.543 e V,价带穿过费米能级,属于半导体的p型掺杂,磁矩降低至38.37μB。
【Abstract】 M-type strontium ferrite is a kind of high-performance permanent magnetic material.Because M-type ferrite has a high coercive force and uniaxial magnetocrystalline anisotropy,good chemical stability and low cost,it can be used in many fields such as aerospace,national defense,industrial manufacturing and electronic devices.With the improvement of the quality of life and the rapid development of industries and national defense,the demand for M-type strontium-barium ferrite increases,and performance requirements become higher and higher.Therefore,researchers have continuously improved its magnetic properties in terms of its preparation methods,process parameters,and new formulations.In recent years,the method of rare earth ion doping has become a hot topic in this field.In this paper,sol-gel self-combustion and chemical co-precipitation methods are mainly used to prepare M-type strontium ferrites with equivalently substituted Sm-Ni and Gd-Ni.X-ray diffractometer(XRD),scanning electron microscope(SEM),vibration sample magnetometer(VSM),and infrared spectrometer(IR)were used to analyze the phase composition,micromorphology,and magnetic properties.Mat Studio is used for modeling and VASP is used for first principles calculation.The stable structure is calculated by optimization,and then the electronic structure characteristics and magnetic properties were calculated after static self-consistency,The experimental and calculation results are as follows:1. Sr1-x(Sm/Gd)xFe12-xNixO19(x=0,0.05,0.1,0.15,0.2)was prepared by chemical co-precipitation.Doped with Sm-Ni:When 0≤x<0.2,it is a single M-type strontium ferrite.When x=0.2,the impurity phases Fe2O3 and Sm Fe O3 appear.The grain shape is approximately hexagonal,and the size is about 80-150 nm.When x=0.15,the saturation magnetization Ms and the residual magnetization Mr reach a maximum of 43 emu/g and 27.06 emu/g respectively.When x=0,the coercive force Hc is a maximum of 6452 Oe,and decreases as the doping amount increases.Doped with Sm-Ni:When 0≤x<0.15,it is a single M-type strontium ferrite.When x=0.15,impurity phases Fe2O3and Gd Fe O3 appear.The grain shape is approximately hexagonal,and the size is about 80-150 nm.At x=0.1,the saturation magnetization Ms and the residual magnetization Mr reach a maximum of 41.04 emu/g and24.73 emu/g.When x=0,the coercive force Hc is a maximum of 6452 Oe and decreases with increasing doping.2. Sr1-x(Sm/Gd)xFe12-xNixO19(x=0,0.05,0.1,0.15,0.2)prepared by sol-gel and self-combustion method.Doped with Sm-Ni:When 0≤x<0.1,it is a single M-type hexaferrite.When x=0.1,impurity phase Fe2O3 appears.The grain shape is a sheet hexagon,part of which is irregular,and size about 120-200 nm.When x=0.05,the saturation magnetization Ms and the residual magnetization Mr reach a maximum of43.71 emu/g and 26.35 emu/g respectively.When x=0,the coercive force Hc is at a maximum of 6620 Oe,and decreases with increasing doping.Doped with Gd-Ni:When x=0,it is a single M-type hexaferrite phase.When x=0.05,the impurity phase Fe2O3 appears.The grain shape is sheet hexagon and irregular sheet,the size is about100-300 nm.When x=0.05,the saturation magnetization Ms and the residual magnetization Mr reach the maximum values of 46.26 emu/g and 28.74 emu/g respectively.When x=0,the coercive force Hc is a maximum of 6620 Oe,and decreases with increasing doping amount.3. The first principles based on density functional theory were used to calculate the M-type strontium ferrite,and the approximate method GGA+U was used to optimize the crystal structure and calculate the properties.The bandgap of Sr Fe12O19was calculated to be 1.681 e V,which was the semiconductor characteristic,and the total magnetic moment was 39.97μB.The stable crystal structure of Sr0.5Sm0.5Fe11.5Ni0.5O19 was calculated.Compared with the undoped,lattice constant is slightly reduced,the band gap was reduced to 0.543 e V and the valence band passes through the Fermi level,indicating that it has a doped P-type semiconductor characteristic.And the magnetic moment was reduced to 38.37μB.
【Key words】 M-type strontium ferrite; Ion doping; magnetism; First-principles; Density functional;