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Rodrigues H.O.,Federal University of Ceara | Rodrigues H.O.,Laboratorio Of Telecomunicacoes E Ciencia E Engineering Dos Materiais | Pires Junior G.F.M.,Federal University of Ceara | Pires Junior G.F.M.,Laboratorio Of Telecomunicacoes E Ciencia E Engineering Dos Materiais | And 8 more authors.
Physica B: Condensed Matter | Year: 2011

In this paper Mössbauer, Raman and dielectric spectroscopy studies of BiFeO 3 (BFO) ceramic matrix with 3 or 10 wt% of Bi 2O 3 or PbO added, obtained through a new procedure based on the solid-state method, are presented. Mössbauer spectroscopy shows the presence of a single magnetically ordered phase with a hyperfine magnetic field of 50 T. Raman spectra of BFO over the frequency range of 100900 cm -1 have been investigated, at room temperature, under the excitation of 632.8 nm wavelength in order to evaluate the effect of additives on the structure of the ceramic matrix. Detailed studies of the dielectric properties of BiFeO 3 ceramic matrix like capacitance (C), dielectric permittivity (ε) and dielectric loss (tan δ), were investigated in a wide frequency range (1 Hz1 MHz), and in a temperature range (303373 K). The complex impedance spectroscopy (CIS) technique, showed that these properties are strongly dependent on frequency, temperature and on the added level of impurity. The temperature coefficient of capacitance (TCC) of the samples was also evaluated. The study of the imaginary impedance (-Z″) and imaginary electric modulus (M″) as functions of frequency and temperature leads to the measurement of the activation energy (E ac), which is directly linked to the relaxation process associated with the interfacial polarization effect in these samples. © 2011 Elsevier B.V. All rights reserved. Source


Rodrigues H.O.,Federal University of Ceara | Rodrigues H.O.,Laboratorio Of Telecomunicacoes E Ciencia E Engineering Dos Materiais | Pires Jr. G.F.M.,Federal University of Ceara | Pires Jr. G.F.M.,Laboratorio Of Telecomunicacoes E Ciencia E Engineering Dos Materiais | And 6 more authors.
Journal of Physics and Chemistry of Solids | Year: 2010

In this paper we studied the effects of Bi2O3 and PbO addition on BiFeO3 (BFO) ceramic matrix. The structural, dielectric and magnetic properties of fifteen BFO samples were discussed in view of possible applications in RF and microwave devices. The present work also reports the preparation of the samples. Polyvinyl alcohol (PVA) and tetraethyl orthosilicate (TEOS) were also added as a binder in the fabrication procedure. The samples have been studied by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and magnetic hysteresis measurements. Further, a study based on impedance spectroscopy also has been done. Dielectric permittivity (ε′) and dielectric loss (tan δ) were measured at room temperature in the frequency range 100 Hz10 MHz, as well as a.c. conductivity. The Im[Z(f)] versus Re[Z(f)] plot has been obtained. The samples were investigated in view of possible applications like miniaturized filters, diplexers and dielectric resonator antennas (DRA). In the RF and MW frequency region, the application of magneto-dielectric and multiferroic perovskite composite materials is desirable for the miniaturization of components. © 2010 Elsevier Ltd. All right reserved. Source

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