Synthesis and characterization of materials based to Al₂O₃-SiO₂ containing Eu³⁺ and silver

The incorporation of rare earth (RE³⁺) ions into small fractions in host matrices has been studied for promoting the appearance of properties related to the RE³⁺ ion of interest. In this sense, the addition of Eu³⁺n suitable host matrices, which have low energy of network phonons, allows the appearance of the phenomenon called photoluminescence, promoting intense emission in the red region of the electromagnetic spectrum when excited in the ultraviolet region. To improve the photoluminescent properties of materials, the introduction of noble metal particles has been emphasizing, an example is the use of silver nanoparticles in a reaction system. The Eu³⁺ has a main emission around 612 nm, (dipole-electric) considered to be hypersensitive to local field changes including those promoted by the presence of silver. The present work sought to obtain and characterize the Al₂O₃-SiO₂ binary system containing Eu³⁺ in the presence and absence of silver synthesized using the sol-gel methodology, varying the molar ratio of Si⁴⁺: Al³⁺ to 90:10, 70:30, 50: 50% in mol respectively and their optical, structural and spectroscopic properties were studied. The amount of Eu³⁺ and silver were fixed at 1 mol% relative to the total number of moles of [Si⁴⁺ + Al³⁺] in the systems. The xerogels were thermally treated at 800, 900, 1000 and 1100 ° C for 4 h. By thermogravimetry (TGA / DTA) the thermal decomposition of the formed materials was analyzed. This technique elucidated the relationship between the increase of the temperature of heat treatment with the elimination of groups suppressors of the intensity of photoluminescence. By Fourier Transform Infrared Spectroscopy (IVTF) we observed bands related to the vibrations of groups such as, Si-O-Si, Al-O, related to the formation of the Al₂O₃-SiO₂ binary system and groups such as OH, CH that can act as suppressors of the photoluminescence of the excited state via non-radiative process. The X-ray diffraction (XRD) results evidenced the formation of the α-Al₂O₃ crystalline phase. The photoluminescence spectroscopy analyzes allowed to observe the incorporation of Eu³⁺ ions in the binary system. All materials obtained in this work showed intense emission in the red region due to the 5D0 → 7F2 transition of Eu³⁺. The lifetime of the excited state was shown to be dependent on the heat treatment temperature and amount of silver. The materials obtained in this work showed great absorption in the ultraviolet region promoting intense emission in the visible region, making them potential candidates for applications in photonic devices (materials that have the ability to act on photons in optical devices). (author)