微量元素Al对La_(0.75)Ce_(0.25)Fe_(11.51)Mn_(0.24)Si_(1.25)H_y合金磁热效应与制冷能力的影响

采用高频悬浮熔炼炉制备了La_(0.75)Ce_(0.25)Fe_(11.51)Mn_(0.24)Si_(1.25)Al_(0.3)和La_(0.75)Ce_(0.25)Fe_(11.51)Mn_(0.24)Si_(1.25)合金样品。样品在0.05 MPa压力、598 K氢气中吸氢至饱和。经X射线衍射及SEM分析La_(0.75)Ce_(0.25)Fe_(11.51)Mn_(0.24)Si_(1.25)Al_(0.3)H_y样品为NaZn_(13)型结构。研究结果表明,在1.5 T磁场下,La_(0.75)Ce_(0.25)Fe_(11.51)Mn_(0.24)Si_(1.25)Al_(0.3)H_y合金样品的等温磁熵变ΔS_M为9.06 J/(kg·K),直接测量的样品绝热温变为2.53 K,均比不含Al元素的La_(0.75)Ce_(0.25)Fe_(11.51)Mn_(0.24)Si_(1.3)H_y略低;但磁熵变ΔS_M和绝热温变ΔT_(ad)的半峰宽δT均大幅提高;同时,合金制冷能力提高。