Phase Composition And Magnetic Properties Of (La,La-Ce-Pr-Nd)(Fe,Co,Si)13 Alloys

In recent years,many researchers have carried out extensive research on magnetocaloric materials,and found that La Fe_13-xSi_xseries alloys show lower cost and larger magnetocaloric effect compared with other magnetic materials.In order to reduce the backlog of light rare earth elements and avoid the harm to the environment caused by the use of a lot of acid and alkali in the separation process of mixed rare earth elements,La-Ce-Pr-Nd mixed rare earth elements without separation were used to replace La in La-Fe-Si alloy.By adjusting the ratio of La-Ce-Pr-Nd mixed rare earth elements to La,and the ratio of Fe to Si,the phase composition and magnetocaloric effect of the alloy were studied.La_1-x（La-Ce-Pr-Nd）_xFe₁₁Co_0.5Si_1.5（x=0,0.2,0.4,0.6,0.8,1.0）alloys were prepared by arc melting.The results show that with the increase of x,in addition to the main phase of Na Zn₁₃cubic structure andα-Fe heterophase,the content of Th₂Zn₁₇rhombic heterophase increases.With the increase of x,the lattice constant of Na Zn₁₃type main phase decreases gradually,and the Curie temperature decreases from 256 K（x=0）to 234 K（x=0.8）.The Arrott curves near Curie temperature indicate that all alloys undergo second-order magnetic transformation,and all alloys show large magnetocaloric effect.For the external magnetic field changes of 0～1 T,0～2 T and 0～3 T,the maximum isothermal entropy changes for x=0.6 alloy are 6.3,11.8 and 14.8J·kg^-1·K^-1respectively.The larger magnetocaloric effect results from the magnetic transformation in the narrow temperature range.The series of alloys（La-Ce-Pr-Nd）₁Fe_13-xSi_x（x=1.5,1.6,1.7,1.8,1.9,2.0,2.1,2.2,2.3,2.4,2.5）were prepared by arc melting and high frequency suspension smelting.The results show that with the increasing Si element substitution,the content of Na Zn₁₃cubic phase increases gradually,and the content of Th₂Zn₁₇diamond phase decreases.When Si content is high,1:2:2 phase is also found in the alloy.With the increase of Si content x,the lattice constant of the Na Zn₁₃phase decreases gradually,and the Curie temperature increases from 210 K（x=2.0）to 229 K（x=2.5）.The Arrott curves near Curie temperature indicate that all alloys undergo second-order magnetic phase transition.The refrigeration temperature region is wide,and there is no hysteresis and thermal hysteresis.In conclusion,the phase composition and magnetic properties of（La,La-Ce-Pr-Nd）（Fe,Si,Co）₁₃alloys containing La-Ce-Pr-Nd were systematically studied.The results show that the Curie temperature of the series of alloys is adjusted to room temperature by doping or substituting elements,and the magnetocaloric effect is large.Therefore,the present research shows great significance to explore the effective ways of magnetic materials.