LaAl添加对放电等离子烧结LaFeSi磁体微观结构和磁热效应的影响

Microstructure and Magnetocaloric Effect of Spark Plasma Sintered LaFeSi Magnets with LaAI Addition

使用LaFe_(11.3)Si_(0.77)薄带合金为前驱体粉末,研究了低熔点La_(0.77)Al_(0.23)合金添加对放电等离子烧结磁体微观结构和磁热性能的影响。研究发现,适量低熔点LaAl合金的添加能够促进包晶反应,制得了具有较高1:13相含量的LaFeSi磁体。磁体中观察到有微弱的巡游电子变磁转变现象的存在。热处理工艺研究显示,退火时间的增加会使得磁体的磁性转变由一级向二级变化,这主要归因于Al向1:13相内部的扩散。1000℃/6 h热处理工艺条件下,其在0~5 T磁场变化下的磁熵变最大,达12.40 J·kg^(-1)·K^(-1),而1000℃/10 h条件下所获得磁体的制冷能力最强,为318.40 J·kg^(-1)。

Using LaFe_(11.3)Si_(0.77)and La_(0.77)Al_(0.23)alloys as precursors,the bulk LaFeSi samples with excellent magnetocaloric performance were synthesized through the spark plasma sintering(SPS)technology.The results show that the La;Al;compound with a low melting point is helpful in facilitating peritectic reaction,and NaZn;-type phase with high content can be achieved.A slight itinerantelectron-metamagnetic transition is observed.The increased thermal annealing time facilitates magnetic transition from the first order to the second order,which is ascribed to the excessive Al diffusion into the 1:13 phase.Under the thermal treatment condition of 1000℃/6 h,the maximum entropy change(-ΔS_(M));of 12.40 J·kg^(-1)·K^(-1)can be obtained,and the highest refrigerating capacity,up to 318.40 J·kg^(-1),is achieved under thermal annealing condition of 1000℃/10 h.