SPS制备Mn_(1.1)Fe_(0.9)P_(0.8)Ge_(0.2)B_x化合物磁热性能的研究

Magnetocaloric Properties in Mn_(1.1)Fe_(0.9)P_(0.8)Ge_(0.2)B_x Compounds Prepared by Spark Plasma Sintering

利用MA＋SPS技术制备Mn1.1Fe0.9P0.8Ge0.2Bx（x=0，0．02，0．03，0．04）化合物并对其晶体结构和磁热性能进行研究。XRD分析结果表明：该系列化合物具有六方Fe：P结构。随着B含量的增加晶格常数a和c均发生了明显的变化，导致c／a的值先减小后增大。分别利用DSC和VSM对材料的磁热性能进行了测试，结果表明居里温度死和熵变均与B的含量存在一个非线性关系，当B的含量为0．02时Mn1.1Fe0.9P0.8Ge0.2B0.02化合物的磁热性能最好，R从x=0时的253K增加到263K，相应的滞后从23K下降到19K，在0～2T外磁场下的磁熵变从28．7J／kg·K增加到32．6J／kg·K。

Mn1.1Fe0.9P0.8Ge0.2Bx （x=0, 0.02, 0.03, 0.04） compounds were prepared by mechanical milling and subsequent spark plasma sintering （SPS） technique. Their crystal structure was investigated by XRD and the magneticaloric properties were measured by DSC and VSM. Results show that Mn1.1Fe0.9P0.8Ge0.2Bx （x=0, 0.02, 0.03, 0.04） compounds possess a hexagonal Fe2P-type crystal structure. The lattice parameters a and c are changed noticeably with the increase of B, and c/a ratio decreases firstly and then increases. There is a nonlinear relationship between Curie temperature as well as the entropy change and the content of B. The compound achieves the best magneticaloric properties in this system when x=0.02. The Curie temperature increases from 253 K for x=0 to 263 K, and thermal hysteresis decreases from 23 K to 19 K. The maximum value of the magnetic entropy change increases from 28.7 to 32.6 J/kg·K for a field change from 0 to 2 T.