PRODUÇÃO E CARACTERIZAÇÃO DE ALUMINOSILCATOS LUMINESCENTES PARA APLICAÇÕES INDUSTRIAIS / PRODUCTION AND CHARACTERIZATION OF ALUMINOSILCATOS LUMINESCENT FOR INDUSTRIAL APPLICATIONS

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

This work aimed the synthesis and characterization of pure and doped calcium aluminosilicates using the proteic sol-gel method and by a new route, which combines the proteic sol-gel method with the solid state synthesis. In the proteic sol-gel method, coconut water (Cocos nucifera) is used as a starting solvent. But for the aluminosilicates synthesis, one of the sources of silicon used was the SiO2, which is not soluble in coconut water. Because of that many procedures were tested to synthesize this material. Therefore it was necessary to propose a new hybrid route that would combine different methodologies to produce ceramic powders. For the usual proteic sol-gel methodology, tetraethylortosilicate (TEOS) was used as the source of Si. In order to determine the best conditions of calcination time and temperature for the different routes of calcium aluminosilicate production, thermal analysis and powder x-ray diffraction (DRX) techniques were used. According to the (DTA) analysis, an exothermic peak at 930C indicates the formation of crystalline phase in the material produced with SiO2. For the one produced whit TEOS, this step is verified around 850C. From the XRD patterns, it was possible to observe the production of the single crystalline phase in both methodologies, however at different calcination temperatures: 1000C for the material produced via sol-gel, with TEOS, and 1300C for the one produced by the hybrid methodology. The crystallite size was evaluated using the Scherrer‟s equation, and the results indicated that the calcined powders in both preparation routes are in nanometric scale. These results were confirmed using the transmission electronic microscopy. Different colorations were observed on the co-doped and calcined doped samples in different conditions. The optical properties of the material were studied and, according to the results obtained using OA, the optical band gap of the Ca2Al2SiO7 system is ~6 ev. It was also observed that the combination of the dopants Ce3+ and Mn2+ indicates an energy transfer process in which the Ce3+ emission, related to the 5d1  4f1 transition, excites resonantly the 6A1(S)  4A1g/4Eg(G) transition of the Mn2+ ion, followed by the emission associated to Mn2+ transitions. Beyond that, the energy level diagram was obtained for the Ce3+ and the transitions associated to the Mn2+ were identified using the Tanabe-Sugano diagram, as a first approximation.

ASSUNTO(S)

hybrid route rota híbrida transferência de energia sol-gel protéico proteic sol-gel method aluminosilicates engenharia de materiais e metalurgica aluminosilicatos energy transfer

ACESSO AO ARTIGO

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