resumo
Glasses with composition xFe(2)O(3)-5MgO-(95 - x)SiO2, where x is equal to 1.25, 2.5, 5 and 10 mol%, were prepared by the sol-gel method. The gel samples were heat-treated at temperature between 500 and 1000 degrees C. The samples were studied using X-ray diffraction (XRD), scanning electron microscopy combined with X-ray microanalysis by energy dispersive spectrometer (SEM-EDS), visible-near infrared spectrometry (VIS-NIR) and dc magnetic measurements. In most samples the presence of magnesium ferrite was detected by XRD. However, in the brown and transparent 1.25Fe(2)O(3)-5MgO-93.75SiO(2) sample heat-treated at 500 degrees C, there was no evidence, by XRD, of the presence of magnesium ferrite. In 10Fe(2)O(3)-5MgO-85SiO(2) composition, heat-treated at 500 and 1000 degrees C, hematite was also present. By the Scherrer method it was determined that the average size of magnesium ferrite crystals, in all the samples heat treated at 1000 degrees C. varied from 8 to 10 nm. All the samples heat treated at 1000 degrees C exhibited ferro or ferrimagnetic interactions combined with superparamagnetism with a blocking temperature. The sample with composition 1.25Fe(2)O(3)-5MgO-93.75SiO(2) treated at 500 degrees C showed a paramagnetic behaviour down to 5K. (C) 2011 Elsevier B.V. All rights reserved.
palavras-chave
LEAD BORATE GLASSES; COMBUSTION REACTION; MGFE2O4; FE; SUSCEPTIBILITY; GD
categoria
Materials Science
autores
da Silva, MGF; Valente, MA
nossos autores
Maria Gracinda Ferreira da Silva
Professor AuxiliarGrupos
agradecimentos
The authors thank Julia Manfroi (Brazilian student) for the help in this research work, CICECO and I3N for the financial support.