112 resultados para Trivalent


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Solid-state Ln(L)(3) compounds, where Ln stands for trivalent Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y and L is 2-methoxybenzoate have been synthesized. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, infrared spectroscopy and complexometry were used to characterize and to study the thermal behaviour of these compounds. The results provided information on the composition, dehydration, coordination mode, structure, thermal behaviour and thermal decomposition.

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Solid-state Ln(L)(3) compounds, where Ln stands for trivalent Tb, Dy, Ho, Er, Tm, Yb, Lu and Y, and L is 3-methoxybenzoate, have been synthesized. X-ray powder diffractometry, infrared spectroscopy, complexometry and elemental analysis were used to characterize the compounds. In order to study the thermal behaviour of these compounds simultaneous thermogravimetry and differential thermal analysis (TG-DTA) and differential scanning calorimetry (DSC) were used. The results provided information on the composition, dehydration, polymorphic transformation, thermal stability and thermal decomposition of the synthesized compounds.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Solid-state Ln(2-MeO-BP) compounds, where Ln stands for trivalent Eu to Lu and Y(III) and 2-MeO-BP (which is 2-methoxybenzylidenepyruvate) have been synthesized. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffraction, infrared spectroscopy and other methods of analysis were used to characterize and to study these compounds. on the base of the obtained results an Ln(2MeO-BP)(3)center dot H2O general formula can be established.

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We present photoluminescence and decay of photo excited conductivity data for sol-gel SnO(2) thin films doped with rare earth ions Eu(3+) and Er(3+), a material with nanoscopic crystallites. Photoluminescence spectra are obtained under excitation with several monochromatic light sources, such as Kr(+) and Ar(+) lasers, Xe lamp plus a selective monochromator with UV grating, and the fourth harmonic of a Nd: YAG laser (4.65eV), which assures band-to-band transition and energy transfer to the ion located at matrix sites, substitutional to Sn(4+). The luminescence structure is rather different depending on the location of the rare-earth doping, at lattice symmetric sites or segregated at grain boundary layer, where it is placed in asymmetric sites. The decay of photo-excited conductivity also shows different trapping rate depending on the rare-earth concentration. For Er-doped films, above the saturation limit, the evaluated capture energy is higher than for films with concentration below the limit, in good agreement with the different behaviour obtained from luminescence data. For Eu-doped films, the difference between capture energy and grain boundary barrier is not so evident, even though the luminescence spectra are rather distinct.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Hydrated lanthanide(III) and yttrium(III) selenites were prepared. Simultaneous thermogravimetric and differential thermal analysis, classical differential thermal analysis, X-ray diffraction and other methods of analysis have been used in the characterisation as well as in the study of the thermal decomposition of these compounds. The results led to the composition and thermal stability and also to interpretations concerning the thermal decomposition mechanisms. © 1990.

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Solid state compounds were prepared of Ln-4-MeO-BP, where Ln is a trivalent lanthanide (except promethium) or yttrium, and 4-MeO-BP is 4-methoxybenzylidenepyruvate. Thermogravimetry-derivative thermogravimetry (TG-DTG), differential scanning calorimetry (DSC) and other methods of analysis have been used to characterize and to study the thermal stability and thermal decomposition of these compounds. © 1993.