Navegando por Autor "Ribeiro, Ulisandra Lima"

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Liquid phase sintering of ferrite of NiCuZn with low magnetic permeability for miniaturization
(Ceramics International, 2018-01) Araújo, José Humberto de; Ribeiro, Ulisandra Lima; Nasar, Ricardo Silveira; Nasar, Marinalva Cerqueira
In this study, we synthesized ferrites with the formula Ni0.5−xCuxZn0.5Fe2O4 and sintered them to x = 0, 0.1, 0.2 and 0.3 using the citrate precursor method. We then analyzed the sintered toroids by X-ray diffraction (XRD) with Rietveld refinement. Scanning electron microscopy (SEM) results showed there to be uniform grains in NiZn, abnormal grains at x = 0.2 with a remnant of the CuO liquid phase, and large grains at x = 0.3. We then analyzed the toroids by vibrating sample magnetometry (VSM). The hysteresis reached a saturation magnetization (Ms) value of 88.37 emu/g and a coercive field (Hc) of 0.0016 T. We calculated the Bohr magnetons using the Ms information and obtained the magnetic permeability with a vector network analyzer (VNA). The toroid with the remnant CuO phase showed relative permeability values of between 20 and 30 and low losses in a wide range of frequencies (10–50 MHz), which we attribute to the microstructure characteristics. Based on our results, this ferrite can be used in the miniaturization of magnetic components used in electro–electronic devices

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