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Title: 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

Abstract

(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 darkmore » 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.« less

Authors:
 [1];  [2]; ;  [2]
  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)
Publication Date:
OSTI Identifier:
22163158
Resource Type:
Journal Article
Journal Name:
Materials Characterization
Additional Journal Information:
Journal Volume: 74; Journal 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); Journal ID: ISSN 1044-5803
Country of Publication:
United States
Language:
English
Subject:
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

Citation Formats

Pozo Lopez, G., E-mail: gpozo@famaf.unc.edu.ar, Instituto de Fisica Enrique Gaviola - CONICET, Condo, A. M., Instituto Balseiro, Universidad Nacional de Cuyo, Av. Bustillo 9500, 8400, San Carlos de Bariloche, Consejo Nacional de Investigaciones Cientificas y Tecnicas, Urreta, S. E., Silvetti, S. P., Aguirre, M. del C., and Instituto de Fisica Enrique Gaviola - CONICET. 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. United States: N. p., 2012. Web. doi:10.1016/J.MATCHAR.2012.08.010.
Pozo Lopez, G., E-mail: gpozo@famaf.unc.edu.ar, Instituto de Fisica Enrique Gaviola - CONICET, Condo, A. M., Instituto Balseiro, Universidad Nacional de Cuyo, Av. Bustillo 9500, 8400, San Carlos de Bariloche, Consejo Nacional de Investigaciones Cientificas y Tecnicas, Urreta, S. E., Silvetti, S. P., Aguirre, M. del C., & Instituto de Fisica Enrique Gaviola - CONICET. 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. United States. doi:10.1016/J.MATCHAR.2012.08.010.
Pozo Lopez, G., E-mail: gpozo@famaf.unc.edu.ar, Instituto de Fisica Enrique Gaviola - CONICET, Condo, A. M., Instituto Balseiro, Universidad Nacional de Cuyo, Av. Bustillo 9500, 8400, San Carlos de Bariloche, Consejo Nacional de Investigaciones Cientificas y Tecnicas, Urreta, S. E., Silvetti, S. P., Aguirre, M. del C., and Instituto de Fisica Enrique Gaviola - CONICET. Sat . "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". United States. doi:10.1016/J.MATCHAR.2012.08.010.
@article{osti_22163158,
title = {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},
author = {Pozo Lopez, G., E-mail: gpozo@famaf.unc.edu.ar and Instituto de Fisica Enrique Gaviola - CONICET and Condo, A. M. and Instituto Balseiro, Universidad Nacional de Cuyo, Av. Bustillo 9500, 8400, San Carlos de Bariloche and Consejo Nacional de Investigaciones Cientificas y Tecnicas and Urreta, S. E. and Silvetti, S. P. and Aguirre, M. del C. and Instituto de Fisica Enrique Gaviola - CONICET},
abstractNote = {(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.},
doi = {10.1016/J.MATCHAR.2012.08.010},
journal = {Materials Characterization},
issn = {1044-5803},
number = Complete,
volume = 74,
place = {United States},
year = {2012},
month = {12}
}