Abstract
Transparent oxyfluoride glass-ceramic films and self-supported layers with composition 80SiO2-20LaF3 doped with Er3+ have been successfully synthesized by sol-gel process for the first time. Crack-free films and self-supported layer with a maximum thickness up to 1.4 µm were obtained after heat treatment at the low temperature of 550 °C for 1 min, resulting in a LaF3 crystal fraction of 18 wt%, as confirmed by quantitative Rietveld refinement. This is the highest value reported up to now for transparent oxyfluoride glass-ceramics prepared by sol-gel. This work provides a new synthesis strategy and opens the way to a wide range of potential applications of oxyfluoride glass-ceramics. The characterization by a wide range of techniques revealed the homogeneous precipitation of LaF3 nanocrystals into the glass matrix. X-ray absorption spectroscopy and electron paramagnetic resonance confirmed that the Er3+ ions are preferentially embedded in the low phonon-energy LaF3 nanocrystals. Moreover, photoluminescence (PL) measurements confirmed the incorporation of dopants in the LaF3 nanocrystals. The effective concentration of rare-earth ions in the LaF3 nanocrystals is also estimated by X-ray absorption spectroscopy.
Highlights
Oxyfluoride glass-ceramics (OxGCs) have attracted great interest in the field of photonics since the pioneering work of Wang and Ohwaki [1]
Data were processed by a Tektronix oscilloscope (Tektronix Inc., Beaverton, OR, USA)
The addition of MTES allows the thickness of films to be increased, compared to when only tetraethyl orthosilicate (TEOS) is used
Summary
Oxyfluoride glass-ceramics (OxGCs) have attracted great interest in the field of photonics since the pioneering work of Wang and Ohwaki [1]. Fujihara et al prepared the first OxGC SG materials in a two-step process [21] involving preparation of silica sol using the classical route followed by mixing of fluoride and RE-ion precursors (acetates, nitrates, chlorides etc.) dissolved in ethanol or acidic medium The mixing of both solutions, with subsequent controlled crystallization, leads to the precipitation of fluoride crystals in the silica-glass matrix. Novel OxGC materials with a much higher active crystal phase content and sintered at a much lower temperature than previously reported have been prepared by taking advantage of the particular benefits of the SG process It was demonstrated how this method leads to precipitation of RE-doped NCs using short heat treatment times. It is shown how most RE ions are incorporated into the NCs during the crystallization process
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