Structure and Magnetic Properties of Porous Ni_(1-x)Zn_xFe_2O_4 Ultrafine Fibers Prepared by Electro spinning Technique

Porous Ni1-xZnxFe2O4(x=0-0.8) ultrafine fibers were prepared by electrospinning technique and subsequent calcination process.The crystal structure,micromorphology,pore character and room-temperature magnetic properties of the samples were investigated by means of XRD,FTIR,FESEM,low-temperature N2 adsorption-desorption and VSM techniques,respectively.The results show that the obtained porous Ni1-xZnxFe2O4 ultrafine fibers calcined at 550℃ for 2 h are single-phase spinel structure with an average grain size of 25-30 nm.These ultrafibers have diameters in the range of 200–500 nm and a large aspect ratio.N2 adsorption-desorption analysis indicate that the pore structure of as-prepared Ni0.5Zn0.5Fe2O4 porous fibers mainly consists of slit-like mesopores with a mean pore diameter of about 11 nm.With the increase of Zn content(x=0 to x=0.8),the lattice constant of Ni1-xZnxFe2O4 ultrafine fibers increases linearly and complies well with Vegard’s law,and the infrared vibrational frequencies corresponding to tetrahedral sites shift toward lower wavenumber.The coercivity of the samples gradually decreases from 13.8 kA/m(x=0) to 2.3 kA/m(x=0.8),whereas the specific saturation magnetization increases initially,reaches a maximun value of 66.8 A.m2/kg at x=0.4 and then decreases with further increase of Zn content.It is found that the synthesized Ni-Zn ferrite untrafine fibers exhibit relatively high coercivity due to their high shape anisotropy compared with the nanoparticle counterparts with similar size.These porous Ni-Zn ferrite untrafine fibers have potential application in many fields such as sensitive devices,microwave absorbers,and catalysts.