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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]

Abstract: Capacitance–voltage and capacitance–frequency characteristics of the metal/n-GaN/metal Schottky contacts with Au, Al and Ag electrodes were investigated as a function of the temperature and external electric field in the frequency range from 100 to 300kHz. Forward capacitance–voltage measurements were carried out in the frequency range from 100Hz to 20MHz. The temperature capacitance coefficient and the electrical tunability were measured as a function of the external DC field for all contacts. The capacitance and dielectric loss measurements show relaxation peaks from 4 to 11kHz for some electrodes, indicating that interfacial effects play an important role in the electrical properties of the GaN Schottky barrier contact. Low-frequency relaxation studies were conveniently used to probe interfacial characteristics of the contacts. [Copyright &y& Elsevier]

In this paper, we will study the effect of the presence of CCTO (CaCu3Ti4O12) in the dielectric permittivity and loss of barium titanate (BTO-BaTiO3) thick films. These films were prepared in two layers geometry using the screen printing technique on Al2O3 substrates. Mechanical alloying followed by the solid state procedure has been used successfully to produce powders of CCTO (CaCu3Ti4O12) used in the films. We also look at the effect of the grain size of the BTO and CCTO in the final properties of the film. These samples were studied using X-ray diffraction, scanning electron microscopy (SEM), Raman and infrared spectroscopies. We also did a study of the dielectric permittivity (K) and loss (D) in the medium-frequency (MF) range (100 Hz–1 MHz), of the films. The role played by firing process in the film preparation and the crystallite size of CCTO and BTO in the dielectric constant and structural properties of the films are discussed. 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]