| Nano ferrite not only has good magnetic properties,but also has magnetocaloric effect,high resistivity,low-frequency loss,and etc.It is widely used in sensor,transformer,photocatalysis,wastewater treatment and biomedicine.Especially in biomedical applications,not only the safety characteristics of ferrite should be considered,but also superparamagnetism and good dispersion should be considered.The particle size distribution and magnetic properties of ferrite will affect its application in these fields.The atomic structure of rare-earth elements is similar,with a variety of electronic energy levels and many excellent optical,electrical,and magnetic properties.Doping rare-earth elements in ferrite will affect the structure and electromagnetic properties of ferrites.Therefore,doping appropriate rare-earth ions in ferrite spinel structure can improve its electromagnetic properties.Rare-earth(Nd,Sm,Gd,Dy,Yb,Sc)doped nano ferrite particles were prepared by chemical co-precipitation method,their structures and magnetic properties were systematically studied.The ferrites were characterized by XRD,ICP-AES,FT-IR,TEM,and PPMS-9.The results are as follows:(1)XRD analysis confirmed that all the samples were cubic spinel structure and single phase.Due to the large radius of rare earth ions,lattice expansion will be induced when rare earth ions enter the ferrite lattice,resulting in the increase of average grain size.TEM showed that the average particle size of NZGd0.07F,MZDy0.02F,and CZSc0.05F were 13.9 nm,10.71 nm and 7.8 nm respectively,which were all larger than the results of XRD.(2)The formation of metal oxides in spinel ferrite structure was confirmed by FT-IR.The octahedron of RE-O,Me–O,and Fe-O and tetrahedron of Fe-O and Zn-O were observed at 419 cm-1 and 570 cm-1,respectively.The concentrations of Ni,Mn,Co,Zn,Fe,and rare-earth elements were determined by ICP-AES,and the results of metal ions were in agreement with the theory.(3)The M-H curves of Ni-Zn ferrites,Mn-Zn ferrites,and Co-Zn ferrites show that rare-earth doped ferrites are superparamagnetic.The magnetization of Sc,Dy,Yb rare-earth doped ferrites are higher than that of Nd,Gd,Sm rare-earth doped ferrites.The highest saturation magnetization of CZYb0.02F is 44.57 emu/g.The results show that the grain size of rare-earth doped ferrite increases and the coercivity increases.(4)The M-T curves of Ni-Zn ferrites,Mn-Zn ferrites,and Co-Zn ferrites show that the magnetic properties decrease with the increase of temperature.The magnetic properties of CZSc0.05F change most with temperature,and the thermal magnetic coefficient KT increases from 0.09 emu/g K to 0.21 emu/g K.The thermal magnetic coefficient KT remains at 0.15 emu/g K in the temperature range of 0-100?.The particle size of CZSc0.05F modified by sodium oleate is 8.8 nm,and the saturation magnetization is 34.46 emu/g,which is suitable to prepare temperature-sensitive ferrofluids.It can be used in heat exchanger,magnetic hyperthermia,switch and other applications close to room temperature. |
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