Sn的加入对MnFe(P,Si)合金显微组织和磁性的影响

Effect of Sn Addition on Microstructure and Magnetism of Mn Fe(P, Si) Alloy

用高能球磨和固态烧结法制备了Mn_(1.3)Fe_(0.7)P_(0.5)Si_(0.5-x)Sn_x(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Fe_2P晶体结构的晶格点阵位置,而是与Mn和Fe形成了Sn_2(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。Mn_(1.3)Fe_(0.7)P_(0.5)Si_(0.5)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/(kg·K),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 refrigera- tion, 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 en- tropy change （-△Sm） peaks at the heating process. This result is in favor of expanding the working tem- perature and refrigerant capacity （RC） of magnetic refrigeration materials. Mn1.3Fe0.7P0.5Si0.5 alloy shows a maximal magnetic-entropy changes （-△Smax） of 12.1 J/（kg.K） in a magnetic field change of 0-1.5 T, a maxi- mal adiabatic temperature change （△Tab） of 2.4 K in a magnetic field change of 0-1.48 T and a thermal hysteresis （△Thyo） of 3 K in vicinity of Curie temperature of 273 K, which can be used as a promising candi- date material for room-temperature magnetic refrigeration applications.