Banca de QUALIFICAÇÃO: SAULO GREGORY CARNEIRO FONSECA
Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.DISCENTE : SAULO GREGORY CARNEIRO FONSECA
DATA : 29/06/2018
HORA: 09:00
LOCAL: Auditório do química 3
TÍTULO:
STRUCTURAL AND MAGNETIC PROPERTIES OF COBALT AND COPPER FERRITES DOPED WITH GADOLINIUM (Gd3+)SYNTHESIZED BY COMBUSTION METHOD
PALAVRAS-CHAVES:
Combustion. Ferrites. Gadolinium. Cationic Distribution
PÁGINAS: 103
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Físico-Química
ESPECIALIDADE: Química do Estado Condensado
RESUMO:
Co and Cu nanoferrites doped with Gd3+ ions, with general formula Co0.5Cu0.5Fe2-xGdxO4 (x = 0, 0.02, 0.04 e 0.06) were synthesized by combustion method and annealed at 900 ºC. The structural properties were determined by Infrared Spectroscopy (FTIR), X-Ray Diffraction (DRX)/Rietveld Method, Scanning Electron Microscopy and the magnetical properties were studied by Vibrating Sample Magnetometer (VSM). FTIR results shows that Gd3+ ions shifts the Fe3+-O2- stretches for lower values. The results of DRX/Rietveld reveal that samples have cubic/spinel structures, additionally ferrites doped with Gd3+ formed a secondary phase (GdFeO3), crystallites sizes of all samples were calculated by Scherrer equation with results in the range between 16.84 – 66.51 nm, it was also found that the measured lattices parameters (a) grows with Gd3+ addition. VSM was used to determine parameters such as MS (Saturation Magnetization), HC (Coercivity), HR (Remanent Magnetization), HR/HC (Squareness), K (Anisotropy Constant) and nB (Bohr Magneton). MS values initially increases reaching the maximum for ferrite Co0.5Cu0.5Fe1.98Gd0.02O4, however, in high concentrations of Gd3+, the Ms values decreases due the cationic migration between octahedral and tetraedrical sites of magnetic spinels, furthermore formation of secondary phase GdFeO3 also decreases the MS values. HC and K increases in larger concentrations of Gd3+, while the HR measured remained approximately constant. Results of HR/HC ratio in the range 0.4-0.3 indicates a magnetic pseudo-single domain formation. Moreover nB’s theorical and experimental values initially grows with additional Gd3+, nevertheless subsequent addition of Gd3+ decreases the values of nB. The nB values are strongly affected by cationic distribution, beyond that, synthesized ferrites shows a soft magnetic behaviour.
MEMBROS DA BANCA:
Presidente - 350633 - ADEMIR OLIVEIRA DA SILVA
Interno - 1308577 - SIBELE BERENICE CASTELLA PERGHER
Externo à Instituição - ELANIA MARIA FERNANDES SILVA - UFRN