[en] Ferroelectric SrBi₂Nb₂O₉ (SBN) thin films were prepared by the polymeric precursors method and deposited by spin coating onto Pt/Ti/SiO₂/Si substrate and crystallized using a domestic microwave oven. It was studied the influence of the heat flux direction and the duration of the thermal treatment on the films crystallization. An element with high dielectric loss, a SiC susceptor, was used to absorb the microwave energy and transfers the heat to the film. Influence of the susceptor position to the sample crystallization was verified, the susceptor was placed or below the substrate or above the film. The SBN perovskite phase was observed after a thermal treatment at 700 deg. C for 10 min when the susceptor was placed below the substrate and for 30 min when the susceptor was placed above the film. Electrical measurements revealed that the film crystallized at 700 deg. C for 10 min, with the susceptor placed below the film, presented dielectric constant, dielectric loss, remanent polarization and coercive field of, 67, 0.011, 4.2 μC/cm² and 27.5 kV/cm, respectively. When the films were crystallized at 700 deg. C for 30 min, with the susceptor placed above the film, the dielectric constant was 115 and the dissipation factor was around of 0.033, remanent polarization and coercive field were 10.8 μC/cm² and 170 kV/cm, respectively

[en] Sr Ti O₃ thin films, obtained by the polymeric precursors method, were obtained by dip coating on Si (111) single crystal substrate and heat treated at 850 deg C X-ray diffraction was used to characterize crystalline phases, lattice parameters and residual stresses with radiation depth penetration. The results showed that residual stresses and crystalline size are dependent on the glancing incident angle. No phase variation was observed with film thickness. (author)

[en] Oriented LiNbO₃ thin films were prepared using a polymeric precursor solution deposited on (0001) sapphire substrate by spin coating and crystallized in a microwave oven. Crystallization of the films was carried out in a domestic microwave oven. The influence of this type of heat treatment on the film orientation was analyzed by X-ray diffraction and electron channeling patterns, which revealed epitaxial growth of films crystallized at 550 and 650 deg. C for 10 min. A microstructural study indicated that the films treated at temperatures below 600 deg. C were homogeneous and dense, and the optical properties confirmed the good quality of these films

[en] Sr Ti O₃ thin films (obtained by polymeric precursors) were dip coated on Mg O (100) monocrystal substrates. After different thermal treatment at 850 deg C, these films were characterized by SEM and, through selective chemical attack, the films were detached from the substrates and characterized by TEM. The results showed that the thermal treatment and the atmosphere influence strongly the crystallization, densification and the grain size of these films. (author)

No abstract available

[en] We report the structural, thermal and magnetic properties of superconducting PrBa₂Cu₃O_7-δ (Pr-123). The existence of superconductivity in samples of Pr-123 is still a polemic subject. To further study this problem, we have measured thin films and high-quality polycrystalline bulk samples by following a sol-gel method, associated with heat treatment in argon atmosphere. The present results confirm the occurrence of superconductivity in Pr-123 polycrystalline and thin film samples

[en] Published in summary form only

[en] Published in summary form only

[en] The knowledge of the percentual composition of phases in calcium aluminate cements and clinkers is of great importance to foresight the behaviour of the cement and refractory concretes made thereof. There are some analytical techniques for these determinations, optical and eletronic microscopy as well as selective chemical attacks, each technique presenting its own difficulties. Using pure phases of CA, CA₂, C₂AS and C₁₂A₇ obtained by electrofusion in a laboratory electric are furnace, calibration curves were developed for X-ray diffratometric determination of phases. The method is very efficient for determination of CA, CA₂, C₂AS and ∝ - A1₂O₃. The determination of C₁₂A₇ presents some variations due to its low concentration in electrofused clinkers. The method finds practical application in quality control of calcium aluminate cements

[en] The identification of corrosive agents and corrosion mechanisms is necessary to increase the furnaces campaign. Silica refractories installed in 'Santa Marina' glass furnace crown were studied. X-ray fluorescence technique was used to determine the corrosive agents diffusion, which are present in the furnace atmosphere, leading to the formation of low melting temperature phases, causing the matrix glassing. Another interesting aspect was observed in the iron oxide/refractories color relation, according to its deepness. Hg porosimetry and X-ray Diffraction were also used to evaluate the microstructural variation and phase changes. (author)