Abstract
Nanocrystalline transparent BaF2:Eu3+ glass-ceramic materials emitting reddish-orange light were fabricated using a low-temperature sol-gel method. Several experimental techniques were used to verify structural transformation from precursor xerogels to sol-gel glass-ceramic materials containing fluoride nanocrystals. Thermal degradation of xerogels was analyzed by thermogravimetric analysis (TG) and differential scanning calorimetry method (DSC). The presence of BaF2 nanocrystals dispersed in sol-gel materials was confirmed by the X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). In order to detect structural changes in silica network during annealing process, the infrared spectroscopy (IR-ATR) was carried out. In particular, luminescence spectra of Eu3+ and their decays were examined in detail. Some spectroscopic parameters of Eu3+ ions in glass-ceramics containing BaF2 nanocrystals were determined and compared to the values obtained for precursor xerogels. It was observed, that the intensities of two main red and orange emission bands corresponding to the 5D0→7F2 electric-dipole transition (ED) and the 5D0→7F1 magnetic-dipole (MD) transition are changed significantly during transformation from xerogels to nanocrystalline BaF2:Eu3+ glass-ceramic materials. The luminescence decay analysis clearly indicates that the measured lifetime 5D0 (Eu3+) considerably enhanced in nanocrystalline BaF2:Eu3+ glass-ceramic materials compared to precursor xerogels. The evident changes in luminescence spectra and their decays suggest the successful migration of Eu3+ ions from amorphous silica network to low-phonon BaF2 nanocrystals.
Highlights
Among the variety of inorganic amorphous host matrices, mixed oxyfluoride glasses in the presence of barium fluoride BaF2 demonstrate a strong potentiality towards the development of near-IR solid-state lasers, broadband fiber amplifiers and highly compact optical devices [1,2,3]
Transparent glass-ceramic materials containing BaF2 fluoride nanocrystals were fabricated by low-temperature sol-gel method and examined using several experimental techniques: thermogravimetric analysis (TG)/differential scanning calorimetry method (DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), EDS, IR-ATR and luminescence spectroscopy
Thermal decomposition of Ba(CF3 COO)2 was identified using TG/DSC measurements, whereas the structural changes in sol-gel silica network were verified by the IR-ATR spectroscopy
Summary
Among the variety of inorganic amorphous host matrices, mixed oxyfluoride glasses in the presence of barium fluoride BaF2 demonstrate a strong potentiality towards the development of near-IR solid-state lasers, broadband fiber amplifiers and highly compact optical devices [1,2,3]. The systematic investigations indicate that several glasses show a better thermal stability, lower phonon energy and weaker OH− absorption coefficient after introduction of BaF2 to the base chemical composition. In consequence, it results in larger stimulated emission cross-sections and longer luminescence lifetimes related to near-IR laser transitions of rare earth ions. The influence of glass-modifier BaF2 on the positions of luminescence bands of rare earth ions and their relative integrated intensities was examined in detail. The previously published works have been well demonstrated that spectroscopic properties of rare earth ions are changed significantly in tellurite [4], phosphate [5], germanate [6,7,8] and borate [9]
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