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In this work we studied the structural and optical properties of lithium tantalate ͑LiTaO 3 ͒ powders doped with Eu 3+ ions. We have examined the different sites occupied by the rare earth ion through the correlation of the DRX data analyzed with the Rietveld method and some spectroscopic parameters derived from the Eu 3+ luminescence. A direct relation was established between the lattice parameters and the "occupation fraction" of Eu 3+ in each LiTaO 3 site. The occupation fraction was set as the relative population of Eu 3+ ions for each site obtained by means of the intensity, baricenter, and the spontaneous emission coefficients of the 5 D 0 → 7 F 0 transitions. We concluded that the unit cell parameter a presents the same behavior of the Eu 3+ occupation fraction in Ta 5+ sites as a function of the Eu 3+ content in LiTaO 3 . The same was observed for the variation in Eu 3+ occupation fraction in the Li + site and the unit cell parameter c with the Eu 3+ content.

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Fluorescent dyes like Rhodamine B (RB) have been used to identify the spatial distribution of adhesive restorative materials in the tooth/restoration interface. Potential effects of the addition of RB to dental adhesives were addressed in the past, but no further information is available on how to determine suitable concentrations of RB in these bonding agents for imaging in the confocal laser scanning microscope. This study provides systematical strategies for adding RB to viscous dental adhesive resins, focusing on the determination of the lowest range of dye concentrations necessary to achieve an acceptable image of the dentin/adhesive interface. It was demonstrated that optimized images of the resin distribution in dentin can be produced with 0.1-0.02 mg/mL of RB in the (tested) adhesives. Our approaches took into account aspects related to the dye concentration, photophysical parameters in different host media, specimen composition and morphology to develop a rational use of the fluorescent agent with the resin-based materials. Information gained from this work can help optimize labeling methods using dispersions of low-molecular-weight dyes in different monomer blend systems.

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In this work we propose the study of the spectroscopy properties and the energy level location of Ce3+ and Pr3+ in Gd2O2S, along with the effects of Ce4+ (Ce2O2S2) incorporation in Gd2O2S and Gd2O2S:Pr3+ in order to understand the formation and position of the associated defects energy levels in relation to the band structure of Gd2O2S and Pr3+ energy levels. Ce‐, Pr3+‐doped and Pr3+,Ce‐doped Gd2O2S were prepared by the sulfidization of a basic gadolinium carbonate with S8 using H2/N2 (3.0/97.0%) and air during the firing of the precursor. Samples were analyzed by X‐ray diffraction in order to guarantee the formation of the Gd2O2S single phase. Diffuse reflectance spectroscopy and luminescent measurements (emission/excitation) were used to locate Ce3+, Pr3+ and defects energy levels in relation to the band structure of Gd2O2S. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)