Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} nanoparticles dispersed in a SiO{sub 2} matrix synthesized by sol-gel processing

Journal Article · Sat Dec 15 00:00:00 EST 2012 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2012.08.010· OSTI ID:22163158

Condo, A. M. ^[1]; Urreta, S. E. ^[2]; Silvetti, S. P.; Aguirre, M. del C. ^[2]

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1. Centro Atomico Bariloche, Comision Nacional de Energia Atomica, Av. Bustillo 9500, 8400, San Carlos de Bariloche (Argentina)
2. Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, Ciudad Universitaria, 5000, Cordoba (Argentina)

(Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4})x/(SiO{sub 2})(100 - x) (x = 5, 20 and 50 wt.%) nanocomposites are synthesized by a sol-gel method using tetraethylorthosilicate (TEOS) and metallic nitrates as precursors, and by further annealing the powders for 1 h at 1273 K. X-ray diffraction (XRD), transmission electron microscopy (TEM), room temperature vibrating sample magnetometry (VSM) and SQUID measurements are employed for structural, morphological and magnetic sample characterization. For all the concentrations analyzed, the powder nanocomposites actually consist of spinel NiZn ferrite nanoparticles, dispersed in an amorphous silica matrix. TEM studies reveal different particle size distributions and particle morphologies for the three ferrite contents. The 20 wt.%-NiZn ferrite samples consist of nearly spherical nanoparticles, of about 8 nm, mainly superparamagnetic, well-dispersed in the amorphous silica matrix, while the 5 wt.%-NiZn ferrite samples exhibit a bimodal particle size distribution (5 and 30 nm) of single-domain nanoparticles embedded in the silica. In the 50 wt.%-NiZn ferrite samples, two particle families are observed: small round superparamagnetic nanoparticles of about 8 nm embedded in the amorphous silica matrix and large, non-spherical, ferrimagnetic ones, forming agglomerates outside the matrix. In all the synthesized samples, thickness fringes are observed inside some of the ferrite nanoparticles in dark field images. This contrast is explained using the theory of electron diffraction in a weak beam dark field (WBDF) condition and considering spherical ferrite nanoparticles. A large range of tailored magnetic properties varying the fraction, dispersion and mean size of the ferrimagnetic NiZn ferrite particles is obtained. Room temperature saturation magnetization values are found in the range 3.0-30.4 Am{sup 2}/kg for the different concentration samples. Coercivity values, between 1.9 and 7.6 mT, are more than 50% higher than those measured in powders of pure stoichiometric NiZn ferrite nanoparticles and somewhat higher than those reported for similar NiZn ferrite/SiO{sub 2} nanocomposites also synthesized by sol-gel processes. A correlation between the nanocomposite microstructure and the observed magnetic properties is established. - Highlights: Black-Right-Pointing-Pointer NiZn ferrite/SiO{sub 2} nanocomposites are successfully synthesized by a sol-gel route. Black-Right-Pointing-Pointer Depending on the NiZn ferrite content single or bimodal size distributions result. Black-Right-Pointing-Pointer Coercivity (1.9-7.6 mT) is 50% higher than in stoichiometric NiZn ferrite powders. Black-Right-Pointing-Pointer Microstructure and magnetic properties are correlated.

• OSTI ID: 22163158
• Journal Information: Materials Characterization, Vol. 74, Issue Complete; Other Information: Copyright (c) 2012 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1044-5803
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COERCIVE FORCE
COMPOSITE MATERIALS
ELECTRON DIFFRACTION
FERRITE
FERRITES
MAGNETIC PROPERTIES
MAGNETIZATION
MICROSTRUCTURE
NANOSTRUCTURES
PARTICLE SIZE
PARTICLES
POWDERS
SILICA
SILICON OXIDES
SOL-GEL PROCESS
SPHERICAL CONFIGURATION
SUPERPARAMAGNETISM
THICKNESS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION