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用机械合金化方法成功制备了Mn1.35Fe0.65P1-xSix(x=0.56和0.57)化合物,分别采用了两种不同的工艺对化合物进行热处理。用X射线衍射仪、振动样品磁强计和绝热温变测量仪分别对样品的结构、等温磁熵变和绝热温变进行了测量。实验结果表明,经过两种不同热处理工艺处理的化合物都形成了Fe2P型六角结构,空间群为P62m,在经过淬火处理的Mn1.35Fe0.65P0.44Si0.56化合物中存在少量的(Mn,Fe)5Si3第二相,空间群为P63/mcm。样品的居里温度都在室温附近,在278～296 K之间变化,不同热处理工艺对化合物的居里温度具有一定的影响。经过淬火处理的化合物存在较小的热滞和较大的等温磁熵变,两种化合物的热滞都由自然冷却处理时的5 K降低到淬火处理时的3 K。当Si的含量分别为0.56和0.57时,与经过自然冷却处理的化合物相比,经过淬火处理的化合物的最大磁熵变分别提升了33%和20%。在经过淬火处理的Mn1.35Fe0.65P0.44Si0.56化合物磁熵变最大,磁熵变的最大值为4.3 J.kg-.1K-1。经过自然冷却处理的Mn1.35Fe0.65P0.44Si0.56化合物的最大绝热温变为1.2 K。低成本的原料、较小的热滞、理想的制冷温区和较大的磁热效应使得Mn1.35Fe0.65P1-xSix这一系列化合物在室温磁致冷方面有应用前景。
The compounds of Mn1.35Fe0.65P1-xSix (x = 0.56 and 0.57) were successfully prepared by mechanical alloying and the compounds were respectively heat-treated by two different techniques. The structure of the sample, isothermal magnetic entropy change and adiabatic temperature change were measured by X-ray diffractometer, vibrating sample magnetometer and adiabatic temperature change measuring instrument respectively. The experimental results show that the Fe2P hexagonal structure and the space group P62m are formed in the compounds treated by two different heat treatment processes. There is a small amount of (Mn, Fe) in the quenched Mn1.35Fe0.65P0.44Si0.56 compound, 5Si3 second phase space group P63 / mcm. The Curie temperature of the sample is around room temperature and varies from 278 to 296 K, and the heat treatment process has a certain influence on the Curie temperature of the compound. The quenched compounds showed less thermal hysteresis and larger isothermal magnetic entropy change, and the thermal hysteresis of both compounds decreased from 5 K in natural cooling to 3 K in quenching. When the Si contents were 0.56 and 0.57, respectively, the maximum magnetic entropy change of the quenched compounds increased by 33% and 20% respectively compared with the naturally-cooled compounds. After quenching the Mn1.35Fe0.65P0.44Si0.56 compounds maximum magnetic entropy change, the maximum magnetic entropy change of 4.3 J.kg-.1K-1. The maximum adiabatic temperature of the naturally-cooled Mn1.35Fe0.65P0.44Si0.56 compound changed to 1.2K. Low-cost raw materials, small thermal hysteresis, ideal cooling temperature and large magnetocaloric effect make Mn1.35Fe0.65P1-xSix this series of compounds have room for magnetic refrigeration applications.