Influence Of Mn,Nd And Melting Add Quantity On Phase And Magnetic Properties Of The LAFE_10.5COSI_1.5 Compounds

LaFe10.5CoSi1.5?LaFe10.5-xMnxCoSi1.5 (x= 0,0.1,0.2,0.3) and La1-yNdyFe10.5CoSi1.5(y= 0,0.1,0.2,0.3,0.4,0.5) alloys of La(Fe, Si)13 system were prepared by electric arc melting. The as-cast compounds were annealed at 1323 K for 10 hours in box-type annealing furnace under vacuum condition. The phase purity and crystal structures of these compounds were analyzed by powder X-ray diffraction, scanning electron microscope and energy disperse spectroscopy; their magnetic properties were performed by using avibrating sample magnetometer.The results show that, when melting add quantity is 5 at.%of La, the NaZn13-type phase is the main phase in LaFe10.5CoSi1.5 compounds, the impurity phases include a small amount of a-Fe and La-rich phase. When melting add quantity are 0%,10 at.% and 15 at.% of La, a large number of a-Fe, LaFeSi and La-rich phase have been observed.Besides a small amount of a-Fe and La-rich phases,1:13 phase is the main phase in LaFe10.5-xMnxCoSi1.5(x= 0,0.1,0.2,0.3) alloys annealed at 1323 K for 10h. With the increase of Mn, the Curie temperature and the maximum magnetic entropy change of these compounds are decrease. Under a magnetic field of 0.05 T, the Curie temperatures Tc determined from the M-T curves when dM/dT reached the peak point are 317 K,302 K,282 K and 262 K, respectively. The maximum magnetic entropy changes are 3.91,3.68,3.20 and 2.88 J/(kg·K) under an applied magnetic field from 0 to 2 T.To La1-yNdyFe10.5CoSi1.5 alloys, when y is 0,0.1, 0.2 or 0.3, NaZn13-type phase are the main phase and only a small amount of ?-Fe and La-rich phases exist. When y increases to 0.4 or 0.5, Nd2Fe15Si2 phase has been ovserved. With the increase of Nd, the Curie temperature of La1-yNdyFe10.5CoSi1.5(y= 0,0.1,0.2,0.3) compounds decrease from 317 K to 306 K. The values of maximum magnetic entropy change increase. Under 0-2 T magnetic field, they are 3.91,4.31,4.74,5.28 J/(kg·K), respectively.