Effect of varying the acid to metal ion ratio R on the structural and magnetic properties of SiO2-doped Ni-Zn ferrite

摘要

A nitrate-citrate-silica gel was prepared from metallic nitrates, citric acid and tetraethoxysilane (TEOS) by sol-gel process with different citric acid to metal nitrates ratio R-2 and it was further used to synthesize Ni0.5Zn0.5Fe2O4/20 wt% SiO2 nanocomposites by auto-combustion. The effect of varying the citric acid to metal nitrates ratio R on the structural and magnetic properties of the composites were studied by IR, Si-29 CP/MAS NMR, XRD, EPR and SQUID measurements. The nitrate-citrate-silica gels exhibited self-propagating combustion behavior, and it directly transformed into nanosized (14-22 nm) NiZn ferrite particles with spinel crystal structure after combustion. The R value in the starting solution affects the magnetic interaction between NiZn ferrite and silica, and then determines the particle size. Further, varying the R value has a direct effect on the EPR parameters (DeltaH(PP), g factor, N-S and T-2) and SQUID parameters (M-s, M-r and H-c) of the as-synthesized powder. (C) 2004 Elsevier Inc. All rights reserved.