Sol-gel synthesis and characterization of single-phase Ni ferrite nanoparticles dispersed in SiO sub(2) matrix

Nanoparticles of NiFe sub(2)O sub(4) dispersed in SiO sub(2) (25 wt%) matrix were synthesized by sol-gel method using tetraethyl orthosilicate (TEOS), as a precursor for SiO sub(2). The sol-gel method for nanocomposites normally provides multi-phase nanoparticles. We investigated by a synopsis of di...

Full description

Saved in:
Bibliographic Details
Published in:Journal of alloys and compounds 2010-03, Vol.493 (1-2), p.385-390
Main Authors: Nadeem, K, Traussnig, T, Letofsky-Papst, I, Krenn, H, Brossmann, U, Wuerschum, R
Format: Article
Language:English
Subjects:
Annealing
Coercive force
Dispersion
Nanoparticles
Particle size
Phases
Silicon dioxide
Sol gel process
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Nanoparticles of NiFe sub(2)O sub(4) dispersed in SiO sub(2) (25 wt%) matrix were synthesized by sol-gel method using tetraethyl orthosilicate (TEOS), as a precursor for SiO sub(2). The sol-gel method for nanocomposites normally provides multi-phase nanoparticles. We investigated by a synopsis of different analysis methods, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and SQUID-magnetometry, how the various chemical phases are transformed to a single-phase spinel structure during the various stages of annealing from 300 to 900 degree C. We have developed a full phase diagram of chemical phases as a function of annealing temperature. The average particle size lies in the range 16-27 nm. The chemical phases formed below 900 degree C are NiFe, NiO, gamma -Fe sub(2)O sub(3), alpha -Fe sub(2)O sub(3), and NiFe sub(2)O sub(4), respectively. The role of the TEOS prepared SiO sub(2) matrix is to restrict the particle size in a small range in order to rule out particle size effects. In the mid-infrared, a shift of the vibrational Fe-O bond is observed from 568 to 586 cm super(-1) for annealing between 500 and 700 degree C which indicates an increasing NiFe sub(2)O sub(4) phase formation. A systematic study of coercivity field (ranging from 32 to 200 Oe) and saturation magnetic moment (ranging from 12.2 to 32.1 emu/g) for differently annealed samples supports our findings about the evolution of single-phase NiFe sub(2)O sub(4) at 900 degree C. The opposite trend of saturation magnetic moment and coercivity with respect to annealing temperature clearly separates the different phases of metallic, antiferromagnetic, and finally single-phase spinel NiFe sub(2)O sub(4).
ISSN:0925-8388
DOI:10.1016/j.jallcom.2009.12.107