Preparation of NiZn ferrite/SiO2 nanocomposite powders by sol-gel auto-combustion method

A nitrate-citrate-silica gel was prepared from metallic nitrates, citric acid and silica powder by sot-gel process, and it was further used to synthesize Ni0.5Zn0.5Fe2O4/SiO2 nanocomposites by auto-combustion. The obtained (Ni0.5Zn0.5Fe2O4)(100-x),(SiO2)(x), (x = 5,10,20 wt%) samples were characterized by IR, DTA-TG, Si-29 CP/MAS NNIR and XRD techniques. The nitrate-citrate-silica gels exhibited self-propagating combustion behavior, and it directly transformed into nanosized (8-16 nm) NiZn ferrite particles with spinet crystal structure after combustion. The content of silica in the starting solution affects the combustion process, and then determines the particle size of the as-synthesized powder. The interaction between NiZn ferrite and silica was investigated through the Si-29 CP/MAS NMR spectra. It was found that a change of chemical shift and band intensity occurs in the Q(3) and Q(4) resonance. (C) 2003 Elsevier B.V. All rights reserved.