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Your search keyword '"Fechine, P.B.A."' showing total 104 results
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104 results on '"Fechine, P.B.A."'

47. Microstructure and magneto-dielectric properties of ferrimagnetic composite GdIG X :YIG1− X at radio and microwave frequencies

Author

Fechine, P.B.A., Pereira, F.M.M., Santos, M.R.P., Filho, F.P., de Menezes, A.S., de Oliveira, R.S., Góes, J.C., Cardoso, L.P., and Sombra, A.S.B.

Subjects
*MICROSTRUCTURE, *DIELECTRICS, *MICROWAVES, *COMPOSITE materials, *GARNET, *MAGNETIC permeability, *FERRIMAGNETISM, *RIETVELD refinement, *X-ray diffraction
Abstract

Abstract: The gadolinium iron garnet (GdIG, Gd3Fe5O12) and yttrium iron garnet (YIG, Y3Fe5O12), and their GdIG X :YIG1− X composites, were obtained by a new solid-state procedure. The microstructure of the samples was studied by X-ray powder diffraction and Rietveld refinement, Vickers microhardness and scanning electron microscopy. The density and microhardness behavior were studied as a function of the lattice parameters for the composite samples. In the present work, the magnetic and dielectric properties of the GdIG X :YIG1− X composite at radio and microwave frequencies were also studied. The magnetic permeability and dielectric permittivity and loss properties for the composite GdIG X :YIG1− X showed good potential for use in components, when one is looking for moderate ε r′ and μ r′ materials with low loss in the radio-frequency and microwave range. [Copyright &y& Elsevier]

Published
2009
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48. Synthesis, structure and vibrational properties of GdIG X :YIG1− X ferrimagnetic ceramic composite

Author

Fechine, P.B.A., Silva, E.N., de Menezes, A.S., Derov, J., Stewart, J.W., Drehman, A.J., Vasconcelos, I.F., Ayala, A.P., Cardoso, L.P., and Sombra, A.S.B.

Subjects
*YTTRIUM iron garnet, *FERRIMAGNETISM, *HYSTERESIS loop, *MAGNETIZATION, *X-ray diffraction, *MOSSBAUER spectroscopy
Abstract

Abstract: Y3Fe5O12 (YIG) crystal has many attractive characteristics, such as low dielectric loss, narrow resonance linewidth in microwave region and also possesses a good saturated magnetization value. Composite technology in general sets out to combine materials in such a way that the properties of the composite are the optimum for a particular application. The different materials work together to give a composite of unique properties. In this work, we present the preparation procedure (obtaining) of the GdIG X :YIG1− X ferrimagnetic ceramic matrix composite by mechanical alloying and calcinations. Besides that, we study its properties by X-ray powder diffraction, infrared, Micro-Raman, 57Fe Mössbauer spectroscopy and hysteresis loop measurements. [Copyright &y& Elsevier]

Published
2009
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50. Dielectric relaxation of BaTiO3 (BTO)–CaCu3Ti4O12 (CCTO) composite screen-printed thick films at low temperatures

Author

Fechine, P.B.A., Almeida, A.F.L., Freire, F.N.A., Santos, M.R.P., Pereira, F.M.M., Jimenez, R., Mendiola, J., and Sombra, A.S.B.

Subjects
*ELECTRIC measurements, *THICK films, *DIELECTRIC relaxation, *LOW temperatures
Abstract

Abstract: In this work, we report electrical measurements of CaCu3Ti4O12 (CCTO) and (BaTiO3–barium titanate, BTO) thick films. The dielectric constant (K) measurements shows that the BTO thick film present a higher K compared to CCTO compound, in the range of frequencies under study. However, for the composite film (CCTO50 and CCTO50T films), one has an unexpected result; the dielectric constant is higher for all the frequencies under study. The BTO–CCTO composite films do not obey the empirical mixing rule. These electric properties were also studied in the temperature range of 80–300K. For the CCTO film, two relaxation processes were detected. The calculated activation energy was around 0.51eV for temperatures above 200K. One second relaxation process was observed on cooling below 200K with activation energy around 0.061eV. For the composite film CCTO50T, both relaxation processes are still present. Therefore, these measurements confirm the potential use of such materials for small high dielectric planar devices. These films are also attractive for capacitor applications and certainly for microelectronics, microwave devices (cell mobile phones, for example), where the miniaturization of the devices is crucial. [Copyright &y& Elsevier]

Published
2006
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