Banca de DEFESA: SAULO GREGORY CARNEIRO FONSECA
Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.DISCENTE : SAULO GREGORY CARNEIRO FONSECA
DATA : 07/08/2018
HORA: 14:00
LOCAL: Sala de aula do Química 1
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: 112
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 calcined at 900 ºC. The structural properties were determined by infrared spectroscopy (FTIR), X ray diffraction (XRD) with refinement by Rietveld method, scanning electron microscopy and the magnetic characteristics were studied by vibrating sample magnetometer (VSM). FTIR results shows that Gd3+cations shift the Fe3+-O2- stretches for low values. The results of XRD with refinement by Rietveld reveal that samples have cubic/spinel structures, additionally ferrites with Gd3+ formed a secondary phase (GdFeO3), crystallites sizes of all samples were calculated by Scherrer equation with results in the range 16,84 to 66,51 nm., either the measured lattices parameters grow with Gd3+ addition. VSM was used to determine parameters such as MS (Saturation Magnetization), HC (Coercivity), HR (Remmanent Field), HR/HC (Squareness), K (Anisotropy Constant) and nB (Bohr Magneton). Althought MS values initially increases, reaching the maximum value for ferrite Co0,5Cu0,5Fe1,98Gd0,02O4, in high concentrations of Gd3+ the Ms decreases, due the cations migrations between octahedral and tetraedrical sites of magnetic spinels, furthermore the formation of GdFeO3 also affects the saturation magnetization of Co0,5Cu0,5Fe1,98Gd0,02O4. HC and K values rise in major concentrations of Gd3+, while the HR measured were almost constant. Results of HR/HC ratio in the range 0,4 to 0,3 indicates a magnetic pseudo-single domain formation, moreover results of theoretical and experimental nBs initially increase with addition of Gd3+, however in higher concentrations of Gd3+ was observed a decrease in nB values, it was proposed that the values of magnetic moments are strongly influenced by cationic distribution and chemical composition of ferrites. The materials synthesized in this work presented characteristics of soft magnetic materials, with possibilities of applications in absorption field of radiation in microwave region.
MEMBROS DA BANCA:
Presidente - 350633 - ADEMIR OLIVEIRA DA SILVA
Interno - 1308577 - SIBELE BERENICE CASTELLA PERGHER
Externo à Instituição - ALINE CARVALHO BUENO - IFRN
Externo à Instituição - ELANIA MARIA FERNANDES SILVA - UFRN
Externo à Instituição - ÉRICO DE MOURA NETO - IFRN