resumo
A Ni-Zn ferrite precursor powder was synthesized by co-precipitation upon adding ammonia to an aqueous solution of the precursor iron, nickel, and zinc nitrate salts. The powder was calcined at a range of temperatures (200-1200 degrees C) and the crystalline phase evolution was assessed by X-ray diffraction coupled with Rietveld refinement. Intermediate phases (NiFe2O4 and Fe2O3) with increasing crystallinity coexisted in the system up to 1000 degrees C. The required Ni0.8Zn0.2Fe2O4 phase could only be attained at 1200 degrees C. The magnetic properties measured using a vibrating sample magnetometer revealed high magnetization saturation level (similar to 59 emu/gm) above 400 degrees C. The coercivity showed a steady decrease with increasing heat treatment temperature, leading to a change from a hard to soft magnetic state. The BET specific surface area and the SEM morphology were found to be dependent on calcination temperature, atmosphere (air or N-2) and on the milling procedure. (C) 2012 Elsevier Ltd. All rights reserved.
palavras-chave
ZINC FERRITE; NANOPARTICLES
categoria
Materials Science
autores
Olhero, SM; Soma, D; Amaral, VS; Button, TW; Alves, FJ; Ferreira, JMF
nossos autores
José Maria da Fonte Ferreira
Professor(a) Jubilado(a)
Susana Maria Henriques Olhero
Professor Auxiliar
Vitor Brás Sequeira Amaral
Professor CatedráticoGrupos
G2 - Materiais Fotónicos, Eletrónicos e Magnéticos
G5 - Materiais Biomiméticos, Biológicos e Vivos
Projectos
Development of microelectromechanical systems by gelcasting - GELMEMS (PTDC/CTM/099489/2008)
agradecimentos
S.M. Olhero thanks to the Foundation for Science and Technology of Portugal (FCT) for the financial support under the grant SFRH/BPD/27013/2006. Soma Das acknowledges FCT for the grant SFRH/BPD/39262/2007. The authors would also like to thank CICECO for the work at the University of Aveiro and FCT for the financial support under the project PTDC/CTM/099489/2008.