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1、摘 要永磁材料常见于发电设备、传感设备的构成之中。目前，研究界致力于开发成本低廉且性能优质的新一代非稀土永磁材料。镧铁硅合金被普遍地接受为实用的室温磁制冷材料，不过它的主相要经过最少一个星期的退火才能得到，且非常难以制得低硅含量的单相。近期，中国科学院下属研究所的稀土磁性功能材料实验室发现了一类富含La元素的非化学计量比成分限值，在这种成分范围内只需几个小时便能够迅速地生成La、Fe、Si主相，其中还因包含了更少的硅含量而具有更好的磁热性能，这一发现将极大提高高性能磁热材料的合成效率。同时研究者通过扩散偶方法，深入且系统性地分析了这类富稀土合金的相，包含它的形成原理、它的形貌与位相之间的关联等
2、，通过这些分析找到了一类二元La5 Si3的过渡相，它能够使主相的生长呈现层片结构，同时缩短扩散的长度来缩短退火的用时。高能效的室温磁制冷相较于以往的气体压缩制冷技术而言有更好的性能。作为富有潜力的候选磁制冷剂材料，镧铁硅系合金大多数磁性转变的情况下将会引起晶格参数等理化性质的改变，这样的改变会在热和磁场循环时造成材料性能和结构的衰退，大大降低了其在实际生产中的应用价值。所以，分析镧铁硅材料磁化疲劳退化、磁制冷时限以及结构衰退等关键性质对于提高这类材料的实用性有非常关键的意义。本文的研究主体主要是La0.7RE0.3(Fe0.88Si0.12)13材料，其中RE代表了铈、镨、钕、钐、钆、铽、镝
3、、钬、铒、镥，本文将围绕这些主题开展分析：针对晶格对称性及常数的相结构分析；针对相变温度、滞后、磁化强度的磁相变特征分析；等温磁熵变效应分析等。研究这些结构与相变的参数、稀土元素的组成部分大小以及电子结构间的相互关联。在此基础上，本文分析了镧铁硅化合物其微观结构因为稀土元素及热处理条件的不同而发生改变的规则。对于镧铁硅化合物的铸态样品而言，其第二相和基体相具有共晶反应的特征，该相将优先被析出而影响到基体相的形成。对于镧铁硅化合物的原始甩带样品而言，其RE值小于等于0.2时基本不会出现析出相；其 RE值在0.4和0.6中间时，析出相会以条形进行排列且大小超过1微米；其RE值大于等于1.0时，析出
4、相会连接在一起呈有序的分布。这次为了获得最佳的磁性能，本文的RE取值为0.3。最后，本文分析了镧铁硅化合物其磁性能因为稀土元素及热处理的不同而发生改变的规则。通过XRD衍射图样来观察经历24小时和1373K热处理后的样品，得到-Fe相衍射峰的含量相较于主相Na Zn13型的相要多出很多的结论，这一结论反映出此种热处理方法并非最优的选择，它未能除去-Fe相从而获得较纯的Na Zn13型1:13相。因此，本文分别在12小时、1273K和4小时、1323K的条件下进行热处理研究，发现最佳的XRD图样是4小时、1323K条件下的结果，从图样中能够发现10种各异的稀土元素样品均能呈现良好的Na Zn13
5、型的1:13相衍射峰和更少的-Fe相衍射峰，能够更好地消除杂项来获取单一的目标相。本文使用的熔炼方法为电弧熔炼，即在4小时、1323K的设定环境中生成以1:13相为主的镧铁硅化合物磁制冷材料。运用了XRD等手段来表现这一化合物的相结构等特征；运用交流磁化率直接测量仪进行镧铁硅合金交流磁化曲线的测量；运用温差突跃法研究了合金的居里温度。通过上述实验获得了以下结论：稀土元素原子质量的变化会导致-Fe 杂相含量的变化，轻稀土则可以显著帮助化合物热处理工艺，以获得成Na Zn13型晶体机构，获得较为纯粹的镧铁硅化合物。在镧铁硅化合物中，如钬、铒等质量较重的稀土元素能够比起铈、镨等质量较轻的稀土显著提高
6、其Tc值，其中，不讨论合金中替代元素硅的含量对于杂相及其 Tad 的作用大小。最后本文得出的结论是：随着稀土原子质量的上升，镧铁硅合金的TC温度会从163K逐步上升至221K。关键词：稀土永磁材料，La-Fe-Si合金，磁相变，居里温度The research of the micro phase structure and magnetic properties of the La(Fe0.88Si0.12)13 alloy with trace rare earth elementsAbstractThe performance of a new generation of non-rar
7、e earth permanent magnet materials. Neodymium iron silicon alloys are generally accepted as practical room temperature magnetic refrigeration materials, but its main phase is obtained through annealing for a minimum of one week, and it is very difficult to obtain single phase with low silicon conten
8、t. Recently, the Laboratory of Rare Earth Magnetic Functional Materials under the Institute of the Chinese Academy of Sciences has discovered a non-stoichiometric compositional limit that is rich in La elements. Within this composition range, La, Fe can be quickly generated in a few hours. The main
9、phase of Si, which also has better magnetocaloric properties because it contains less silicon, will greatly improve the synthesis efficiency of high-performance magnetocaloric materials. At the same time, the researchers used the diffusion couple method to deeply and systematically analyze the phase
10、 of this type of rare earth-rich alloy, including its formation principle, its morphology, and the correlation between the phases. Through these analyses, we have found a class of binary La5Si3 transition phase, which can make the main phase growth layer structure, while shortening the diffusion len
11、gth to shorten the annealing time.Energy-efficient room temperature magnetic refrigeration has better performance than previous gas compression refrigeration technology. As a potential candidate for magnetic refrigerant materials, most magnetic transitions of silicon-iron-silicon-based alloys will c
12、ause changes in the physicochemical properties such as lattice parameters, which will result in material properties and structure during thermal and magnetic field cycling. The recession has greatly reduced its application value in actual production. Therefore, the analysis of the critical propertie
13、s of magnetization fatigue degradation, magnetic refrigeration time limits, and structural degradation of yttrium iron silicon materials is of crucial importance for improving the practicality of such materials.The main research subject of this paper is La0.7RE0.3(Fe0.88Si0.12)13 material, in which
14、RE stands for lanthanum, lanthanum, lanthanum, lanthanum, lanthanum, lanthanum, lanthanum, lanthanum, lanthanum, lanthanum, and this article will focus on these themes. Carry out analysis: phase structure analysis for lattice symmetry and constant; magnetic phase transition characteristic analysis f
15、or phase transition temperature, hysteresis, magnetization; isothermal magnetic entropy change effect analysis. The interrelationships between these structural and phase transition parameters, the size of the rare earth elements, and the electronic structure were studied.On this basis, this paper an
16、alyzes the rules for the change of the microstructure of silicon-iron-silicon compounds due to different rare earth elements and heat treatment conditions. For an as-cast sample of a niobium iron silicon compound, the second phase and the matrix phase have the characteristic of eutectic reaction, and this phase will be preferentially precipitated to affect the formation of the matrix phase. For the original slug-band material of the niobium-iron-silicon compou
