片状La_(0.9)Ce_(0.1)Fe_(11.7-x)Mn_xSi_(1.3)氢化物的高气压合成及磁热效应研究

High-pressure synthesis of plate-shaped La_(0.9)Ce_(0.1)Fe_(11.7-x)Mn_xSi_(1.3) hydride and study of its magnetocaloric effect

La（Fe,Si）_（13）氢化物被认为是最具有应用前景的室温磁制冷工质之一,主动磁蓄冷样机上使用的理想磁制冷工质通常要求为片状块体。本工作在高达40 MPa的高压氢气气氛下烧结制备了片状La_（0.9）Ce_（0.1）Fe_（11.7-x）Mn_xSi_（1.3）（x=0,0.29,0.35,0.41）氢化物块体。X射线衍射分析表明,片状氢化物由具有立方NaZn13结构的La（Fe,Si）13相及少量α-Fe相构成,其晶格常数比母合金明显增加。Mn的掺杂有利于抑制烧结过程中α-Fe的析出,并且使样品的居里温度降低至室温附近。在0~2T的外磁场下,片状La_（0.9）Ce_（0.1）Fe_（11.35）Mn_（0.35）Si_（1.3）氢化物块体的磁熵变ΔSm在289K时达到最大值4.3J/（kg·K）。

La（Fe,Si）13 hydride is regarded one of the most promising room-temperature magnetic refrigerants.A typical active magnetic refrigerator machine requires thin plate-shaped refrigerants.In this work,La0.9 Ce0.1-Fe11.7-xMnxSi1.3（x=0,0.29,0.35,0.41）hydrides were prepared by sintering in a high-pressure H2 atmosphere of 40MPa.The X-ray diffraction analysis reveals that the plate-shaped La（Fe,Si）13 hydrides consist of NaZn13-type structure with a small amount ofα-Fe as impure phase,and that the lattice constants of NaZn13 phase remark-ably increase after hydrogenation.Meanwhile,Mn-doping is beneficial for restraining the precipitation ofα-Fe, and reduces the Curie temperature to around room temperature.La0.9 Ce0.1 Fe11.35 Mn0.35 Si1.3 thin plate-shaped hy-dride shows a magnetic-entropy changeΔSm of 4.3 J/（kg.K）for a field change of 2 T at 289 K.