Synthesis and characterization of NiZn ferrite / SiO2 nanocomposites

G. POZO LÓPEZ; S.P. SILVETTI; M. DEL C. AGUIRRE; A.M. CONDÓ

Ariston Hotel Convention Center. Rosario. Argentina

Congreso; 10th Inter-American Congress of Electron Microscopy 2009 (CIASEM 2009) - 1st Congress of the Argentine Society of Microscopy (SAMIC 2009); 2009

Sociedad Argentina de Microscopía (SAMIC)

Nanostructured NiZn ferrite and silica ((NiZnFe2O4)0.5/(SiO2)0.5) nanocomposites were synthesized by three different methods: sol-gel, wet impregnation of nitrates in powders of amorphous silica and wet impregnation of powders previously ball-milled with amorphous silica. The as-prepared samples were then annealed for 1 hour at 1000°C in air atmosphere. The resulting microstructures were characterized by X-ray diffraction techniques and by transmission electron microscopy. The room temperature magnetic hysteresis properties were also investigated. The sample synthesized by sol-gel was found to contain spherical NiZn ferrite particles, homogeneously embedded in the amorphous silica pores, with a narrow distribution of diameters (~10 nm). Large particles (30-80 nm) were also found on the surface of these composite grains. The sample synthesized by the wet impregnation of nitrates presented a broad size distribution of ferrite grains (10-100 nm). Small quantities of other phases, as hematite and willemite, were also detected. Finally, in the sample synthesized by impregnation of powders previously milled only NiZn ferrite nanoparticles were present, with a broad size distribution; some particles were embedded in the amorphous SiO2 matrix (smaller particles ~10 nm) and others formed agglomerates (large particles 30-110 nm). All samples displayed hysteresis indicating that the magnetic behavior is governed by the large ferrite particles.