中、低温区磁热效应材料的研究

发布时间：2018-03-19 06:26

本文选题：稀土金属间化合物　切入点：磁热效应　出处：《河北工业大学》2014年博士论文　论文类型：学位论文

【摘要】：磁制冷技术因其绿色环保、高效节能等优点而备受关注，具有广泛的应用前景。为促进磁制冷技术的广泛应用，探索具有优秀磁热性能的磁制冷材料具有重要的意义。本文研究了Fe3C型的Er3-xGdxCo、MgZn2型的Er1-xGdxCoAl、ZrNiAl型的(TmNi1-xCuxAl和HoNi1-xCuxIn)、ThCr2Si2型的RCu2X2(R=Er, Ho和X=Si, Ge)及CrB型的TmGa稀土金属间化合物的磁性和磁热效应，得到的主要结果如下。 1. Er3-xGdxCo (x=0-3)化合物相变温度随着Gd的增加向高温移动，-ΔSM基本上是减小的趋势，但是RC并不是单调变化的，Er1.5Gd1.5Co化合物的RC最大。在磁场变化5T时RC达到629J/kg，因为Gd替代出现了两个连续的相变，拓宽了半峰宽。 2. TmNi1-xCuxAl和HoNi1-xCuxIn的XRD数据精修结果表明，在HoNi1-xCuxIn中键长的不同引起了Cu具有选择性的替代Ni，这种替代方式对材料的相变有重要的影响。在TmNi1-xCuxAl中不存在选择性替代，但是晶格参数随着Cu含量的变化在x=0.6和x=0.65之间出现了跳跃。随着Ni被Cu替代，Tm的磁矩从平面逐渐向c轴转动，这种变化引起了相变温度及磁性的变化。 3.在TmNi1-xCuxAl (x=0-1)系列化合物中TmCuAl呈现出的磁热效应最大。当磁场变化为5T时，得到最大-ΔSM为24.3J/kg K。当磁场变化为1T和2T时，-ΔSM分别为12.2J/kg K和17.2J/kg K。另外，在磁场变化2T和5T时，最大-ΔTad分别为4.6K和9.4K。当磁场变化为5T时，HoNi0.7Cu0.3In的最大-ΔSM为20.2J/kg K，RC为356.7J/kg。当磁场变化为2T时，，HoNi0.9Cu0.1In的最大-ΔSM为12.5J/kg K，RC为132J/kg。当HoNi0.9Cu0.1In和HoNi0.7Cu0.3In化合物以1:1比例均匀混合，在磁场变化0-2T时，最大-ΔSM为9.4J/kg K，而RC提高到147J/kg，这是因为两相混合拓宽了制冷温区。 4. RCu2Si2和RCu2Ge2(R=Ho, Er)都是反铁磁材料，TN都在10K以下，HoCu2Si2和ErCu2Si2在TN以上均存在着自旋玻璃。ErCu2Si2呈现出大的磁熵变，当磁场变化5T时ErCu2Si2最大的-ΔSM达到了22.8J/Kg K，RC为166.5J/kg。特别是当磁场变化1T和2T时，最大-ΔSM分别为8.3J/kg K和15.8J/kg K。大的-ΔSM值主要来自于磁场诱导的AFM-FM变磁转变。 5. TmGa具有两个连续的磁相变，即PM-AFM和AFM-FM相变。在AFM区域存在场诱导的AFM-FM变磁转变。TmGa具有大的磁热效应，当磁场变化为1T和2T时，最大-ΔSM分别为12.9J/kg K和20.7J/kg K；RC分别为69J/kg和149J/kg。另外，在磁场变化为1T和2T时ΔTad分别为3.2K和5K。
[Abstract]:Magnetic refrigeration technology has attracted much attention because of its advantages of green environment protection, high efficiency and energy saving, and has wide application prospects. In order to promote the wide application of magnetic refrigeration technology, It is of great significance to explore magnetic refrigeration materials with excellent magnetocaloric properties. The magnetic and magnetocalorimetric effects of Er3-xGdxCoMgZn2, Er1-xGdxCoAlNiAl, TmNi1-xCuxIntroy and RCu2X2Si2 RCu2X2R, Ho) and CrB type TmGa rare earth intermetallic compounds have been studied in this paper. The main results are as follows. 1. The phase transition temperature of Er3-xGdxCo + XN 0-3) compounds shifted to high temperature with the increase of Gd. But RC is not the largest RC of Er1.5Gd1.5Co compound with monotonic variation. When the magnetic field changes 5T, RC reaches 629J / kg, because the Gd substitution has two consecutive phase transitions and widths the width of the half peak. 2. The refinement results of XRD data of TmNi1-xCuxAl and HoNi1-xCuxIn show that the difference of bond length in HoNi1-xCuxIn leads to the selective substitution of Ni in Cu, which has an important effect on the phase transition of the material. There is no selective substitution in TmNi1-xCuxAl. However, with the change of Cu content, the lattice parameters jump between x0. 6 and x0. 65. With the magnetic moment of Ni replaced by Cu gradually turning from plane to c axis, the change of phase transition temperature and magnetism is caused by the change of lattice parameters. 3. TmCuAl exhibits the largest magnetocaloric effect in the TmNi1-xCuxAl series. When the magnetic field changes to 5T, the maximum 螖 SM is 24.3J / kg K. when the magnetic field changes to 1T and 2T, the 螖 SM is 12.2J / kg / kg K and 17.2J / kg / kg K respectively. In addition, when the magnetic field changes 2T and 5T, The maximum 螖 Tad was 4.6K and 9.4K, respectively. When the magnetic field changed to 5T, the maximum value of HoNi0.7Cu0.3In was 20.2J / kg KN RC = 356.7J / kg. When the magnetic field changed to 2T, the maximum value of HoNi0.9Cu0.1In was 12.5J / kg KRC = 132J / kg.When HoNi0.9Cu0.1In and HoNi0.7Cu0.3In compounds were mixed uniformly at 1: 1, when the magnetic field changed 0-2T, The maximum-螖 SM is 9.4 J / kg Kand while RC increases to 147 J / kg, which is because the two-phase mixing widens the refrigeration temperature range. 4. Both RCu2Si2 and RCu2Ge2Ge RU Ho, er) are antiferromagnetic materials. There exists a large magnetic entropy change in spin glass, ErCu2Si2 and ErCu2Si2 both below 10K. When the magnetic field changes 5T, the maximum -螖 SM of ErCu2Si2 reaches 22.8JKg / KG RC = 166.5J / kg. especially when the magnetic field changes 1T and 2T, respectively. The maximum-螖 SM is 8.3J / kg K and 15.8J / kg K, respectively. 5. TmGa has two continuous magnetic transitions, namely, PM-AFM and AFM-FM. There is a great magnetocaloric effect on the field-induced AFM-FM magnetoconversion in the AFM region. When the magnetic field changes to 1T and 2T, the maximum 螖 SM is 12.9J / kg K and 20.7 J / kg KNRC are 69J / kg and 149J / kg, respectively. In addition, when the magnetic field changes to 1T and 2T, the maximum 螖 SM is 12.9 J / kg K and 20.7 J / kg KNRC are 69 J / kg and 149 J / KG, respectively. When the magnetic field changes to 1T and 2T, 螖 Tad is 3.2k and 5Krespectively.
【学位授予单位】：河北工业大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TB64

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