Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/63381
Type: Artigo de periódico
Title: Nanometric particle size and phase controlled synthesis and characterization of gamma-Fe2O3 or (alpha plus gamma)-Fe2O3 by a modified sol-gel method
Author: Silva, MF
de Oliveira, LAS
Ciciliati, MA
Silva, LT
Pereira, BS
Hechenleitner, AAW
Oliveira, DMF
Pirota, KR
Ivashita, FF
Paesano, A
Pastor, JM
Perez-Landazabal, JI
Pineda, EAG
Abstract: Fe2O3 nanoparticles with sizes ranging from 15 to 53 nm were synthesized by a modified sol-gel method. Maghemite particles as well as particles with admixture of maghemite and hematite were obtained and characterized by XRD, FTIR, UV-Vis photoacoustic and Mossbauer spectroscopy, TEM, and magnetic measurements. The size and hematite/maghemite ratio of the nanoparticles were controlled by changing the Fe:PVA (poly (vinyl alcohol)) monomeric unit ratio used in the medium reaction (1:6, 1:12, 1:18, and 1:24). The average size of the nanoparticles decreases, and the maghemite content increases with increasing PVA amount until 1:18 ratio. The maghemite and hematite nanoparticles showed cubic and hexagonal morphology, respectively. Direct band gap energy were 1.77 and 1.91 eV for A6 and A18 samples. Zero-field-cooling-field-cooling curves show that samples present superparamagnetic behavior. Maghemite-hematite phase transition and hematite Neel transition were observed near 700K and 1015 K, respectively. Magnetization of the particles increases consistently with the increase in the amount of PVA used in the synthesis. Mossbauer spectra were adjusted with a hematite sextet and maghemite distribution for A6, A12, and A24 and with maghemite distribution for A18, in agreement with XRD results. (C) 2013 AIP Publishing LLC.
Country: EUA
Editor: Amer Inst Physics
Rights: aberto
Identifier DOI: 10.1063/1.4821253
Date Issue: 2013
Appears in Collections:Unicamp - Artigos e Outros Documentos

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