掺杂对W型六角晶系铁氧体的微观结构和磁性能研究

发布时间：2018-03-03 16:22

  本文选题：W型铁氧体　切入点：陶瓷法　出处：《安徽大学》2017年博士论文　论文类型：学位论文

【摘要】：目前以SrO·6Fe_2O_3为代表的磁铅石型六角晶系铁氧体即M型铁氧体已成为铁氧体烧结磁体的主流,对于该M型铁氧体磁体,人们着眼于使铁氧体晶粒粒径接近单磁畴粒径、使铁氧体晶粒在磁晶各向异性方向上保持一致以及使烧结体高密度化,继续进行着高性能化的研究。该研究的结果是M型铁氧体磁体的特性接近其上限,其磁性能也很难飞速的提高。作为可能表现出比M型铁氧体磁体性能更高的铁氧体磁体中,熟知的有W型铁氧体。W型铁氧体磁体比M型铁氧体磁体的饱和磁化高10%左右,其各向异性磁场程度相同,而且W型铁氧体具有2个阳离子晶位,可进行多种2价阳离子或3价阳离子替换,能够比M型铁氧体更广泛的改变磁性。因此需要找到高性能且稳定的永磁材料,W型铁氧体就是其中一个重要的方向。W型铁氧体具有较大的饱和磁化强度、较强的磁晶各向异性、化学性能稳定等优点,已被广泛应用于磁光材料及磁记录、微毫米波段材料和永磁材料领域。W型铁氧体的磁性能的改善可以通过掺杂取代来实现。本论文采用溶胶-凝胶法和固相反应法制备离子掺杂取代的系列W型铁氧体样品。样品的微观结构利用X射线衍射仪(XRD)、X射线光电子能谱仪(XPS)和扫描电子显微镜(SEM)进行表征,样品的磁性能利用振动样品磁强计(VSM)和永磁材料自动测量装置进行表征。具体的实验结果如下:1.采用溶胶-凝胶法制备了非稀土离子Ca掺杂取代的W型铁氧体Ba1-xCaxCo_2Fe16027(x = 0,0.1,0.3,0.4和0.5),并研究热处理温度和Ca含量对其微观结构和磁性能的影响。XRD结果证明适量Ca离子掺杂取代的铁氧体均为单一、稳定的纯相。取代后产物的晶胞参数a几乎不变,而晶格参数c减小,晶胞体积V减小,导致晶格收缩变形,这一晶格畸变行为意味着Ca离子成功进入晶体晶格中,SEM观察到所有样品都有着较好的六方结构,颗粒基本上分布均匀。随着取代量x的增加,样品的比饱和磁化强度σs增大,在x = 0.50时有最大值σs=63.6A·m2/kg,说明钙的掺杂量越大磁体的磁性能越好。2.采用固相反应法制备了不同La~(3+)掺杂的W型铁氧体Ba_(1-x)La_xZn_2Fe_(16)O_(27)Cx=0-0.25),并研究了 La含量对其微观结构和磁性能的影响。XRD结果显示,当x≤0.20时样品是单一的磁铅石型W相,然而当x=0.25时,La_2O_3相出现。样品形成了六角片状结构,而且颗粒分布均匀。随着La~(3+)掺杂含量的增加,样品的晶格常数a和c不断减小,导致晶胞体积V也随着减小,同时空隙率增加。样品的饱和磁化强度Ms先增加后减小,当轻稀土 La~(3+)取代量x=0.10时,样品的饱和磁化强度Ms达到峰值71.38emu/g,较未掺杂样品的饱和磁化强度提高约22.1%。其矫顽力Hc先增加后减小再增大。X射线光电子能谱研究结果分析表明,取代前Fe分别主要以Fe~(3+)三价态存在,取代后,可以看出有La~(3+)谱存在,而Fe则以Fe~(3+)(三价)+Fe2+(二价)混合价态的形式存在。利用X射线光电子能谱证实了 La~(3+)离子取代能使部分Fe~(3+)离子转变成Fe2+离子。这表明La能进入W型铁氧体的A位,并且显著提高样品的磁性能。3.采用固相反应法制备了不同Gd~(3+)离子掺杂的W型铁氧体BaFe~(2+)2Fe~(3+)_(16-x)Gd_xO_(27)(x=0-0.20),并研究了热处理的干燥温度和烧结温度对Fe2W铁氧体样品相结构的影响,以及Gd~(3+)离子掺杂含量对铁氧体样品微观结构和磁性能的影响。对于干燥温度的影响,当干燥温度为170℃时有Fe3O4相出现,干燥温度180-200℃可以获得单一的磁铅石型相,干燥温度为210℃时样品中除了Fe2W相结构,同时还有一些M型铁氧体和α-Fe_2O_3的相。对于烧结温度的影响,当烧结温度在1100℃时,样品中除了 Fe2W相结构,同时还有一些M型铁氧体相。在此条件下获得W单相的铁氧体,适宜的烧结温度为1120-1200℃。对于Gd~(3+)离子含量的影响,当x0.15时样品是单一的磁铅石型W相,然而当x=0.20时,Gd2O_3相出现。SEM显示样品形成了六角状结构。随着Gd~(3+)离子掺杂含量的增加,样品的晶格常数a和c均增大,导致晶胞体积V也随着增大。X射线光电子能谱显示取代后有Gd~(3+)离子谱存在。当Gd~(3+)离子掺杂含量x从0增加到0.05时,样品的饱和磁化强度(Ms)、剩磁(Br)和最大磁能积[(BH)max]均增大,x从0.05增加到0.15时,随后减小。当Gd~(3+)离子掺杂含量x从0增加到0.10时,内禀矫顽力(Hcj)和磁感应矫顽力(Hcb)均增,x从0.10增加到0.15时,随后减小。这说明Gd~(3+)离子能够进入W型铁氧体晶位中,并且明显改变其磁性能。
[Abstract]:Magnetoplumbite type six angle crystal ferrite at SrO and 6Fe_2O_3 as the representative of the M has become the mainstream of ferrite sintered ferrite magnet, ferrite magnet for the M, people focus on the ferrite grain size close to single domain size, the ferrite grain is consistent and the sintered body of high density in the magnetocrystalline anisotropy direction, continue to carry out the research of high performance. The results of this study are the properties of M type ferrite magnets close to its upper limit, its magnetic properties are difficult to rapidly increase. The ferrite magnets as may exhibit than M ferrite the magnet performance higher, with about W ferrite.W ferrite magnet than M ferrite magnets with high saturation magnetization of 10%, the same degree of anisotropy of magnetic field, and W ferrite with 2 cationic sites, for a variety of 2 divalent cations or 3 divalent cations can replace. The change of magnetic M ferrite is more than enough widely. So we need to find a permanent magnetic material with high performance and stable, W ferrite is one of the important direction of.W ferrite has larger saturation magnetization, magnetic anisotropy is strong, has the advantages of stable chemical properties, has been widely used in magneto optical materials and magnetic recording, magnetic field of micro millimeter band material and permanent magnet material.W ferrite can be improved by substitution to achieve. This paper adopts W series ferrite sol-gel method and solid-state reaction method for preparing substituted ion doped samples. The microstructure of the body by using X ray diffraction (XRD), X ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) properties of the samples were characterized by vibrating sample magnetometer (VSM) and permanent magnet material automatic measuring device was investigated. The specific results are as follows 1.: sol gel W ferrite Ba1-xCaxCo_2Fe16027 non Ca doped rare earth ions substituted by (x = 0,0.1,0.3,0.4 and 0.5), ferrite and Research on heat treatment temperature and the influence of Ca content on the microstructure and magnetic properties of the.XRD results show that the amount of Ca ions substituted for a single, stable pure phase. After replacing the lattice parameters of the products a is almost the same, while the lattice parameter C decreases, the cell volume of V decreases, cause the lattice contraction deformation, the lattice distortion behavior means that Ca ions successfully enter the crystal lattice, SEM observed that all the samples have six good particle structure, basically evenly distributed. With the increase of substitution amount of X, specific saturation magnetization increase of s samples, at x = 0.50 has the maximum value. S=63.6A m2/kg, it shows that the magnetic doping calcium more magnets can better.2. by solid-state reaction method to prepare La~ (3 different +) W ferrites doped with Ba_ (1-x) La_xZn_2Fe_ (16) O_ (27) Cx=0-0.25), and to study the effect of La content on the microstructure and magnetic properties of.XRD showed that when x is less than or equal to 0.20 when the sample is magnetoplumbite type W single phase, however, when x=0.25, La_2O_3. Samples form six angle sheet structure, and uniform particle distribution. With the increase of doping content of La~ (3+), the lattice constants A and C decreases, resulting in cell volume V with decreased and porosity increased. The saturation magnetization Ms of samples increased first and then decreased, when the light rare earth La~ (3+) to replace the amount of x=0.10, the saturation magnetization Ms samples reached the peak of 71.38emu/g, compared with the undoped saturation magnetization of the samples increased by about 22.1%. the coercivity of Hc increase first and then decrease and then increase.X X-ray photoelectron spectroscopy study results show that replacing the former Fe respectively to Fe~ (3+) trivalent state, 鍙栦唬鍚，

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