Low temperature chemical synthesis of Ni-Zn ferrite nanoparticles

Ferrite nanoparticles of the composition Ni_0.65Zn_0.35 Fe₂ O₄ were prepared by low temperature sol-gel synthesis method using metal nitrates in poly vinyl alcohol (PVA) and in citric acid (CA) matrixes independently to estimate the influence of synthesis matrix on the structural and magnetic parameters of this high saturation magnetization Ni-Zn ferrite composition. Appropriate amounts of metal nitrates were dissolved first in minimum amounts of deionized water to produce clear cationic solutions and then either PVA or CA was added in 1:1 ratio while stirring to form a highly viscous gel. The dried gels were then heat treated at 350°C for 1 h to find them burnt out in a self propagating combustion manner to form loose powders. The resulting powders were characterized by X-ray diffraction, transmission electron microscopy and vibrating sample magnetometer techniques. The sol-gel in PVA sample resulted in fine particle size while the sol-gel in citric acid sample displayed higher magnetization close to that of its bulk value. The lattice constant, magnetization and corecivity of these samples have a direct bearing with the corresponding average crystallite size. The results are analyzed in terms of the core-shell behaviour of the nanoparticles.