B掺杂(Mn,Fe)_2(P,Ge)化合物晶体结构、微观形貌及磁热性能的研究

Crystal Structure,Micromorphology and Magnetocaloric Properties of B Doped (Mn,Fe)_2(P,Ge) Compound

主要研究了B元素替代对Mn_(1.1)Fe_(0.9)P_(0.78)Ge_(0.22)化合物结构、微观形貌和磁热性能的影响.采用机械合金化和固相烧结等技术制备Mn_(1.1)Fe_(0.9)P_(0.78-x)Ge_(0.22)B_x(x=0,0.02,0.04,0.06)系列化合物.利用PANalytical-Empytrean型X-射线衍射仪、VersaLab、TM3030Plus TabletopMicroscope型扫描电镜研究了该系列化合物的结构,磁热性能及微观形貌等.结果发现:所有化合物均为Fe_2P型六角结构.随着B元素替代量的增加,化合物的晶格常数c呈现先增大后减小的趋势,晶格常数a先减小后增大.经EDS分析发现部分B元素进入替代位或间隙位.所有化合物经历由铁磁态向顺磁态的相变,居里温度先降低后增大,热滞明显减小,磁熵变较原样品增大.B元素的替代对MnFePGe磁性和磁热性能有积极的影响.

The effects of B doping on the micromorphology,crystal and magnetocaloric properties of Mn1.1 Fe0.9 P0.78 Ge0.22 compound have been studied.The Mn1.1 Fe0.9 P0.78-xGe0.22 Bx(x=0,0.02,0.04 and 0.06)series of compounds were prepared by using mechanical alloying and solid state sintering techniques,and their microscopic morphology,crystal and magnetocaloric properties were studied using TM3030 Plus Tabletop Microscope,PANalytical-Empytrean X-ray diffractometer,and Quantum-Design VersaLab.The results show that crystallization of all compounds is the Fe2 P-type hexagonal structure.With increase of B content,the lattice constant c first increases and then decreases,and the lattice constant afirst decreases and then increases.EDS analysis indicates that some of B element enters the substitution or interstitial site.All the compounds undergo a ferromagnetic-paramagnetic(FM-PM)state phase transition.The Curie temperature decreases first and then increases,while the thermal hysteresis decreases significantly.B-doped compounds show a larger magnetic entropy change than that of the Boron-free one.All these features show that the B doping has a positive effect on the crystal and magnetocaloric properties of Mn-Fe-P-Ge compound.