Caixa Postal 6007

Fortaleza, Brazil

Caixa Postal 6007

Fortaleza, Brazil
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Oliveira P.W.S.,Caixa Postal 6007 | Oliveira P.W.S.,Federal University of Ceará | Pires Junior G.F.M.,Caixa Postal 6007 | Pires Junior G.F.M.,Instituto Federal Of Educacao | And 4 more authors.
Journal of Microwaves, Optoelectronics and Electromagnetic Applications | Year: 2017

This paper describes an experimental and numerical investigation of the dielectric resonators based on the MgTiO3 ceramic matrix, which relates to their dielectric properties in microwave. The resonators are compounds of the MgTiO3 added with 4, 6, 8, 10 and 12 wt% of the CaCu3Ti4O12. The manufacturing process of the resonators is based on the solid-state method. The properties of the permittivity and dielectric loss are elucidated using the Hakki and Colemans method. The experimental measurements of the dielectric resonators, acting as antennas, provide some results as return loss, gain, efficiency, bandwidth and input impedance. These results are coherent with the numerical investigation. The addition of the perovskite CaCu3Ti4O12 in the MgTiO3 ceramic matrix increased the value of the dielectric constant and it was obtained a higher value of 21.01 for the sample MgTiO3 added with 12% CaCu3Ti4O12. The temperature coefficient of resonant frequency (?f) was measured for all the samples and the best value obtained was 9.62 ppm/°C for the sample MgTiO3 added with 12% CaCu3Ti4O12. The material duly proposed, shows to be promising for applications as dielectric antennas and this study point out that it is possible to obtain a dielectric resonator antenna (DRA) with a temperature coefficient of resonant frequency close to zero. © 2017 SBMO/SBMag.


Oliveira R.G.M.,Caixa Postal 6007 | Romeu M.C.,Caixa Postal 6007 | Costa M.M.,Laboratorio Of Telecomunicacoes | Costa M.M.,Federal University of Mato Grosso | And 5 more authors.
Journal of Alloys and Compounds | Year: 2014

The effects of different additions of Bi2O3 (0, 2, 5 and 10 wt.%) on Na2Nb4O11 ceramics have been studied by complex impedance spectroscopy analysis. The structural and dielectric properties of Na2Nb4O11ceramics with Bi2O3 additions are also discussed as a possible material for microwave and radio frequency applications. Solid state reaction method was used for producing the target compound. The present work also reports on sample preparation, where polyvinyl alcohol was used as a binder to reduce the brittleness and the organic binder was burnt out during sintering process. X-ray diffraction at room temperature was used to identify phases formed as well as optimum calcinations conditions the production of Na2Nb 4O11 powder. Analysis was carried out to identify the pure-phase specimen by Rietveld refinement method. Based on this method a structure with the lattice parameters (a = 10.840 Å, b = 6.162 Å and c = 12.745 Å; α = 90, β = 106.4 and γ = 90) was found. The dielectric and electrical properties of Na2Nb4O 11 for appropriate amounts of Bi2O3 additions has showed a considerable enhancement and overriding applications for microwave and radio frequency communications. The electrical behavior (complex impedance Z*, complex modulus M*) were studied over a frequency range (1 Hz to 1 MHz) and temperature (553-713 K). © 2013 Elsevier B.V. All rights reserved.

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