Er_(2-x)Ce_xFe_(17)金属间化合物的磁熵变特性研究

Study on Characteristics of Magnetic Entropy Changes in Er_(2-x)Ce_xFe_(17) Intermetallic Compounds

在氩气气氛中用熔炼法制备了Er2-xCexFe17（x=0，0．05，0．08，0．1，0．15，0．2，0．3，0．4）化合物，通过粉末X射线衍射和SQUID磁强计研究了样品的结构、磁性和磁熵变。结果表明，Er2-xCexFe17化合物具有Th2Ni17型六方结构，通过成分微调使其居里温度处在室温附近。Er2-xCexFe17化合物的λ形（-△SM）-T曲线表明其在居里点附近发生的相变属于二级相变，它使化合物可在较宽温区范围内保持较大的磁熵变。当x=0．05-0．15时，Er2-xCexFe17化合物在2．0和5．0 T外场作用下的最大磁熵变达到金属Gd的40-50％，且其化学性质稳定、制冷温区宽、价格低廉，是一类性价比较高、应用潜力较大的新型低场室温磁制冷工质材料。

A series of Er2-xCexFe17 （x =0,0.05,0.08,0.1,0.15,0.2,0.3,0.4） compounds were prepared by arc melting under purified argon atmosphere. Structure, magnetic properties and magnetic entropy changes of Er2-xCexFe17 compounds were investigated by means of X-ray diffraction pattern and SQUID magnetometer. The results show that the crystal structure is Th2Ni17-type hexagonal for Er2-xCexFe17 compounds, and the Curie temperature of Er2-xCexFe17 compounds can be shifted to room temperature around by a small adjustment of composition. The typical λ-shape （ - △SM）-T curves of Er2-xCexFe17 compounds indicate that the phase transition near Curie temperature belongs to a second order one which conduces the compounds with larger magnetic entropy changes in a comparatively wide range of temperature. With the Ce content x between 0.05 and 0.15, the Er2-xCexFe17 compounds have a higher magnetic entropy changes and the maximal values are about 40 - 50% of the highest magnetic entropy changes of pure metal Gd in external field of 2 or 5 T. Er2-xCexFe17 compounds are potential working media for magnetic refrigeration due to their stable chemical properties, wide temperature range for magnetic refrigeration and low cost.