掺杂Sn对(La, Ce)(Fe, Al, Si)13 合金磁热效应和相变性质的影响

Effect of Sn Doping on Magnetocaloric Effect and Phase Transition Properties of (La, Ce)(Fe, Al, Si)13 Alloys

摘要:

研究了磁制冷材料La_0.75Ce_0.25Fe_11.5-xAl_0.2Si_1.3Sn_x（x=0，0.05，0.1，0.2）的磁热效应和相变性质。X射线衍射结果表明，随着Sn掺杂浓度的增加，主相1:13相减少，α-Fe和LaFeSi相增加。引入密度泛函理论，结合实验结果得出，增加Sn掺杂浓度能够增大晶格常数，并增强相邻原子之间的交换相互作用，从而提高居里温度。当磁场变化为2 T时，体系中最大磁熵变为13.59 J·kg^-1·K^-1，其相对制冷能力为154 J/kg，具有成为磁制冷材料的潜力。通过Banerjee准则和等温熵变的场相关指数n确定当Sn掺杂浓度为0.05%（质量分数）时，合金由一级相变转变为二级相变。合金的相变行为对Sn含量非常敏感，可以通过调节Sn掺杂浓度，实现多级串联制冷。

Abstract:

The magnetocaloric effect and phase transition properties of La_0.75Ce_0.25Fe_11.5-xAl_0.2Si_1.3Sn_x (x=0, 0.05, 0.1, 0.2, wt%) alloys were investigated. X-ray diffraction results show that with increasing the Sn doping content, the content of 1:13 main phase is decreased, and the content of α-Fe and LaFeSi phases is increased. By combining the density functional theory with experimental results, it is found that increasing the Sn doping content can increase the lattice constant and enhance the exchange interactions between adjacent atoms, thereby increasing the Curie temperature. When the magnetic field is 2 T, the maximum magnetic entropy change in the system is 13.59 J·kg^-1·K^-1 and its relative cooling power is 154 J/kg, showing great potential as magnetic refrigeration material. Based on the Banerjee criterion and the field dependence index n of isothermal entropy change, it is concluded that when the Sn doping content is 0.05wt%, the first-order phase transition changes to the second-order phase transition of the alloy. The phase transition behavior of the alloy is very sensitive to the Sn content, and multi-stage series refrigeration can be achieved by adjusting the doping content.