【作者】 袁兰英；

【导师】 甘树才；

【作者基本信息】 吉林大学 ， 分析化学， 2004， 硕士

【摘要】 随着现代工业和现代科学技术的飞速发展，人类进入了一个蓬勃发展的应用高新技术时代，电子装备也已广泛应用于人们的日常生活中，特别是移动通信、计算机、家用电器的日益普及，严峻的电磁环境已成为人们普遍关注的问题，电磁污染成为继水、空气污染后的又一重要环境污染，严重影响着人们的身心健康，因此研制出性质优良的吸波材料具有十分重要的意义。铁氧体吸波材料是利用铁氧体在高频电磁场作用下产生较大磁损耗的原理而制成的一种新型吸波材料，它具有高电阻率和高介电性能，高频时具有较高的磁导率，所以它成为高频、弱电领域研究的一个热点。铁氧体材料的类型主要为：尖晶石型、石榴石型和磁铅石型。随着微波技术的发展，亚毫米波的重要性越来越明显，一般尖晶石型和石榴型铁氧体已经不能满足要求，必须寻求新的铁氧体旋磁材料，这就是磁铅石型铁氧体，它对于高频、超高频电磁波辐射具有很好的吸收效果，其中W型铁氧体是应用最为广泛的一种吸波材料，它属于软磁材料，具有较低的剩余磁感应强度和矫顽力，具有频带宽、磁导率高和随磁场变化较大等特点，因此作为微波吸收材料在较高的频段内被大量应用。此外，稀土元素具有优良的吸波特性，在W型六方铁氧体中加入适量的稀土元素，可以改善其磁特性和微波吸收特性。 首先，本文主要研究了合成磁铅石W型铁氧体材料的新技术路线，用高温固相法制备出了W型六方铁氧体材料，通过实验，确定了合成W型铁氧体的最佳烧结温度和烧结时间为1250℃／3h。并按同样的方法制备出了加入稀土元素的W型六方铁氧体Ba_1-xRE_xCO₂Fe₁₆O₂₇（RE=La、Nd、Sm），且对合成的铁氧体材料进行了结构表征，确定了在保持W型铁氧体结构不变条件下，稀土元素La、Nd、Sm的最大加入摩尔系数x分别为W型稀土铁氧体Bal一xRExC处Fel6027的合成及性能表征0 .20、0.25、0.25。 其次，对所合成的W型铁氧体材料进行磁性测试，由其磁化强度、剩磁性、矫顽力等磁性参数的测试结果分析可知，在保持W型铁氧体结构不变的情况下，稀土元素（La、Nd、Sm）的加入对铁氧体材料的磁性特征没有产生明显的影响，其磁滞回线的形状也始终保持大致相似;而当稀土元素（La、Nd、Sm）的加入量引起了W型铁氧体的结构变化时，其磁化强度、顽磁性、矫顽力等磁性参数均发生了显著的变化。由此分析可以得出，W型铁氧体的磁化强度、顽磁性和矫顽力等表征磁性材料磁特性的参数与铁氧体内部结构有着非常密切的关系，即若铁氧体的结构发生了变化，相应地，其内部磁结构也发生变化，从而其表征磁性材料磁特性的各参数也将发生显著的变化。 最后，对制备的W型铁氧体材料的微波吸收性能进行表征。通过测试其复介电常数的￡r‘、￡，一‘，和复磁导率的pr’、pr“与测试频率的关系可知，其复介电常数的￡「‘、￡r‘，均是随着测试频率的增加而变小;复磁导率的协。’也是随着测试频率的增加而下降，而pr“则是先随着测试频率的增加而有一定程度的增加，达到一定的峰值后又随测试频率有一定的下降趋势，因此p「‘，一f的图谱上，在测试频率为2.OGHz左右处呈现一明显的共振峰。进一步分析稀土元素加入量的不同对其复介电常数的￡ E。‘，和复磁导率的抖;’、”r”的影响可知，当稀土元素的加入量为某个适当数值时，其复介电常数的￡r‘、E、一“均随着稀土元素加入量的增加大致呈上升趋势;复磁导率的比’随着稀土元素的加入量的增加而下降，而协，’’则是随着加入量的增加大致呈上升趋势。最后通过表征其吸波特性的损耗角的正切tg6的值发现，W型铁氧体材料对0.5一14.OGHZ频段内的电磁波具有很好的吸收效果，且由于稀土元素（La、Nd、Sm）的加入，均很大程度上提高了W型铁氧体的微波吸收性能。在稀土元素La、Nd、片扩‘才学2004窟切活学少子甘丈可W型稀土铁氧体Ba!一xRExCoZFel6q7的合成及性能表征S;n的加入摩尔分数X=0 .20时，铁氧体具有最大的损耗角正切值，约为未加稀土元素时tg6值的2.7倍。但值得指出的是，当稀土元素Nd和sm的加入摩尔分数x=0 .25时，虽然在XRD衍射谱图中没有反映出明显的变化，但是，表征吸波特性的损耗角的正切值降低非常明显。因此，可得出这样的结论:接关系，稀土W型铁氧体的微波吸收特性与其加入稀土元素的量有着直即当稀土元素的加入量为某个适合数值时，达一个最高值，而当稀土元素的加入量继续增大时，其微波吸收性能己到即使其结构没有发生完全变化，但稀土W型铁氧体的微波吸收性能己呈现下降趋势。这主要是由于稀土元素加入量的不同对W型铁氧体内部磁结构产生的影响有很大不同，从而使它的吸波性能发生显著的变化。更多还原

【Abstract】 With the rapid development of the modern industry and technology, the humankind has entered a flourish period with the application of the new technology. Electronic products have already been applied to the daily life of people, especially with the increasing popularization of home appliances, communication equipment and data-processing devices, the electromagnetic wave radiation becomes more and more serious and will become the problem people are popularly concerned about. The electromagnetic wave radiation turns into an important environment pollution after the water and air pollution, and it does great harm to the humankind. So the absorbing material has important implications in the field of radar and electromagnetic compatibility and it is very necessary to find a fine microwave absorbing material. Currently in this field people are interested in the use of the hexagonal ferrite-based microwave absorber to act as an absorbing material and provide absorption over a wide bandwidth. Ferrite is a very important class of magnetic material; more especially it is a metal oxide, which contains magnetic ions arranged in such a manner that it produces spontaneous magnetization while maintaining good dielectric and magnetic properties. The hexagonal-type ferrite absorbs microwave energy by lossy interaction of the magnetic field of the wave with their individual magnetization. The hexagonal ferrite materials are suitable for absorbing materials due to a significant value of permeability, low value of coercivity and planar anisotropic behavior in microwave frequencies. There are several types of hexagonal ferrites denoted as M, W and Y phases having complex crystal and magnetic structures. The Ba ion can be removed by rare earth ions and the magnetization was reported to be decreased with increasing amount of the substitution of rare earth ions. The presence of barium ion and the slightly peculiar structure causes the barium hexaferrite to have high magnetic and microwave absorbing properties unlike spinel and garnet.Notwithstanding, the magnetic anisotropy, the magnetic and microwaveabsorbing properties of the barium hexagonal ferrite can be further improved by the external doping a certain amount of rare earth ions (La, Nd, Sm).Firstly, the new preparation technique of the W-type hexagonal ferrite has been investigated in this chapter, and the W-type hexagonal ferrite samples have been prepared by the well-known solid state reaction method. By means of many experiments, finally it is found that the samples were sintered at 1250 for 3 h may as well. A series of rare earth ferrite samples of Ba,.RECoFeO with RE = La, Nd, Sm and x =0. 00, 0. 05, 0. 10, 0. 15, 0. 20, 0. 25, 0. 30, were also prepared by a solid state reaction method. Then the structures of the synthesized samples doped with rare earth ions were observed by X-ray diffraction, and the maximum of the doped coefficient x is 0. 20, 0. 25 and 0. 25 respectively, on condition that the structures of the rare earth W-type hexagonal ferrites have no any change.Secondly, magnetic measurements of the samples were carried out by the magnetic detector, and it is found that the substitution of a certain amount of the rare earth ions in the W-type hexagonal ferrites have no distinct effect on magnetic properties under the condition of unchanging their structures at all times, therefore the shape of the hysteresis curves also has no any change. On the contrary, if the structure of the W-type hexagonal ferrite changes due to the doped rare earth ions, accordingly, the parameters of its magnetic characteristics such as magnetization, retentivity and coercivity were also various prominently. So it has been found that the magnetic properties of the W-type hexagonal ferrites have a great connection with the interior structure of the ferrites.Finally, microwave absorbing properties of the synthesized samples have been described in the end of the paper. By analyzing the relation of the absorbing wave parameters (complex permittivitty and complex magnetic perme更多还原