Abstract
SrBi2Ta2O9 (SBT) is a bismuth-layered perovskite that finds application as thin film for nonvolatile random-access memories and as high temperature ceramic transducer. The synthesis of SBT by the solid-state reaction requires high temperatures (Tsimilar to1000degreesC), at which bismuth losses are significant, leading to non-stoichiometric compositions with decreased properties. To overcome this drawback, lower temperature reactions of organic precursors have been reported for the production of this oxide. This work describes a novel method to obtain SBT powders that uses Ta2O5 as starting reagent. The thermal behaviour of the SBT precursor gel obtained by this new method is compared to other SBT precursors: those produced by a sol-gel method starting from alkoxides reagents and those related to conventional solid-state reaction. The new method combines the advantage of using reagents that are less toxic and less expensive than alkoxides with the possibility of producing SBT at lower temperatures than those required by the conventional route.

Abstract
SrBi2Ta2O9 (SBT) is a bismuth layered perovskite (BLP) with interesting ferroelectric properties for memories applications. The previous study on the synthesis of seeded and unseeded SBT thin films by the authors G. Gonzalez Aguilar, M.E.V. Costa, I.M. Miranda Salvado, J. Eur. Ceram. Soc. 25 (2005) 2331] has shown an increase of the crystallinity of the films and an improvement of the thin film ferroelectric properties when using SBT seeds. However, the detailed role of the seeds as an improver of the thin film properties has not been investigated so far. In the present work we study the role of the seeds, particularly with respect to the reactions between film and (bottom) underlying platinum electrode. The comparison of the results obtained by characterizing the seeded and unseeded thin films via Rutherford backscattering (RBS) and particle induced X-ray emission (PIXE) techniques reveals an effective modification of the substrate-thin film interface by the presence of the seeds. Moreover, the evaluation of the thin film ferroelectric properties by atomic force microscopy (AFM) shows an improvement of the local piezoelectric hysteresis loops by the seeds. These seeding effects as well as those observed in non-stoichiometric SBT thin films with different bismuth contents are used to discuss the barrier-like role of the SBT seeds against reactions between film and the platinum electrode and its contribution to the improvement of the thin film properties.

Abstract
In this work a theoretical and experimental analysis of the spectrum of methylene blue is made in order to clarify the nature of the shoulder appearing at similar to 620 nm. This shoulder has been several times attributed to the existence of an hypothetical methylene blue chiller. The results here obtained do not agree with the existence of such a dimeric specie, and point out differences in the ionic strength of the solution as the phenomenon responsible for the variations observed in these spectra.

Abstract
The growth of SrBi2Ta2O9 (SBT) films on top of Pt electrode substrates is an important issue for the fabrication of ferroelectric based memories. In a recent publication, SBT thin films grown using seeded and unseeded procedures were studied by PIXE and RBS. Difficulties and misfits found in the comparison of results from both techniques were, at that time, overcome by physical considerations. These, although not rendering interpretation impossible, left out the possibility of understanding the exact nature of the differences between the interface behavior in each case. In the present work it is shown that the reanalysis of the same data using the recently developed RBS-PIXE simultaneous and self-consistent calculation present in NDF leads to stronger conclusions on the solid state reaction occurring during the deposition stage for both types of samples. Allowing for the occurrence of solid state reactions between the deposited film and the Pt electrode even in the case of seeded samples leads to a full explanation of IBA data, this result showing that in complex systems such as this, the PIXE data are essential and must be integrated with the RBS data in an holistic analysis, in order to properly unfold the depth profile of the samples. Contrary to what is usually supposed PIXE data is therefore shown to contain hidden depth structure information.

Abstract
This work proposes different kind of solid-contact graphite-based electrodes for the selective determination of sulphonamides (SPHs) in pharmaceuticals, biological fluids and aquaculture waters. Sulfadiazine (SDZ) and sulfamethoxazole (SMX) were selected for this purpose for being the most representative compounds of this group. The template molecules were imprinted in sol-gel (ISG) and the resulting material was used as detecting element. This was made by employing it as either a sensing layer or an ionophore of PVC-based membranes and subsequent potentiometric transduction, a strategy never reported before. The corresponding non-imprinted sol-gel (NISG) membranes were used as blank. The effect of plasticizer and kind/charge of ionic lipophilic additive was also studied. The best performance in terms of slope, linearity ranges and signal reproducibility and repeatability was achieved by PVC membranes including a high dielectric constant plasticizer and 15 mg of ISG particles. The corresponding average slope was -51.4 and -52.4 mV/decade, linear responses were 9.0 x 10(-6) and 1.7x10(-5) M, and limits of detection were 0.74 and 1.3 mu g/mL for SDZ and for SMX, respectively. Good selectivity with log Kpot< -0.3 was observed for carbonate, chloride, fluoride, hydrogenocarbonate, nitrate, nitrite, phosphate, cyanide, sulfate, borate, persulphate, citrate, tartrate, salicylate, tetracycline, ciprofloxacin, sulphamerazine, sulphatiazole, dopamine, glucose, galactose, cysteine and creatinine. The best sensors were successfully applied to the analysis of real samples with relative errors ranging from -6.8 to +3.7%.

Abstract
Among the different materials studied for ferroelectric applications, SrBi2Ta2O9 (SBT) and SrBi2Nb2O9 (SBN) have deserved a particular interest for the production of non-volatile random access memories (NVFRAMs) due to their fatigue endurance propel-ties. However, the high temperatures required for obtaining these Aurivillius compounds in a straightforward way make necessary to search alternative procedures to synthesize them. In this work the approach of using SBT seeds to improve the synthesis of SBT thin films by a sol-gel procedure is studied and their effects on the thin film properties are evaluated. XRD and SEM analysis of the obtained seeded and unseeded thin films, annealed at different temperatures, show that the use of SBT seeds lowers the crystallization temperature of the perovskite phase and affects the thin film microstructure inducing the development of well defined and more elongated grains. Dielectric and ferroelectric properties are also improved by the seeding procedure. The characteristics of the seeded films annealed at 720 degrees C for 20 min show that the present technique has the advantage of requiring smoother annealing conditions than currently reported methods for producing films with comparable characteristics.