用高能球磨和固态烧结法制备了Mn1.3Fe0.7P0.5Si0.5-xSnx (x=0、0.02、0.04,原子分数)系列合金,系统研究了Sn的加入对合金显微组织、磁性和磁热效应的影响。结果表明,所有合金中都存在少量的(Fe, Mn)3Si相,在含Sn的合金中,Sn原子并没有进入到Fe2P晶体结构的晶格点阵位置,而是与Mn和Fe形成了Sn2(Mn, Fe)相。Sn的加入也使合金中形成了2种成分的(Fe, Mn)2(P, Si)相,导致样品在升温过程中出现2次铁磁-顺磁转变,对应为2个连续磁熵变峰,从而有利于合金磁制冷温区的扩展和制冷容量的提升。Mn1.3Fe0.7P0.5Si0.5合金具有优异的室温磁热效应,1.5 T磁场变化下的最大磁熵变为12.1 J/(kgK),最大绝热温变为2.4 K,合金的热滞为3 K,Curie温度为273 K,可作为室温磁制冷的理想候选材料。
This decade has brought an immense interest in room temperature magnetic refrigeration, because it is considered as a type of potential energy saving material and friendly to environment. MnFe(P, Si) magnetic refrigerants materials shows high-performance and relatively low-cost, which paves the effective way for commercialization of magnetic refrigeration and magnetocaloric power-conversion. The present work is devoted to investigating the effect of Sn addition on microstructure, magnetism and magnetocaloric effect on MnFe(P, Si) alloy. Mn1.3Fe0.7P0.5Si0.5-xSnx (x=0, 0.02, 0.04, atomic fraction) alloys were prepared by mechanical alloying (MA) and solid-state reaction methods. The results show that Sn atoms do not enter into the lattice position of Fe2P. The Sn2(Mn, Fe), (Fe, Mn)3Si, Si-riche (Fe, Mn)2(P, Si) and P-riche (Fe, Mn)2(P, Si) matrix phase are formed in Sn-containing alloys. Two different compositions of (Fe, Mn)2(P, Si) phase result in two ferromagnetic-paramagnetic phase transition and two magnetic entropy change (-ΔSm) peaks at the heating process. This result is in favor of expanding the working temperature and refrigerant capacity (RC) of magnetic refrigeration materials. Mn1.3Fe0.7P0.5Si0.5 alloy shows a maximal magnetic-entropy changes (-ΔSmax) of 12.1 J/(kgK) in a magnetic field change of 0~1.5 T, a maximal adiabatic temperature change (ΔTad) of 2.4 K in a magnetic field change of 0~1.48 T and a thermal hysteresis (ΔThys) of 3 K in vicinity of Curie temperature of 273 K, which can be used as a promising candidate material for room-temperature magnetic refrigeration applications.