Effect of dopant precursors on the optical properties of rare‐earths doped oxyfluoride glass‐ceramics. Issue 7 (14th October 2019) - Gorni, Giulio
Abstract: The crystallization of fluoride nanocrystals (NCs) in chemically and mechanically stable aluminosilicate glasses has shown interesting optical properties even for small crystal fractions (10‐15 wt%). When rare‐earth (RE) ions are used as dopants, crystal‐like features can be reproduced and an increase in the emission and/or energy transfer processes, with respect to the starting glasses, is observed. A crucial point for these materials is the study of the local surrounding of RE ions and their incorporation in the NCs. In fact, the effective concentration in the NCs can be much higher than the nominal concentration, up to one order of magnitude or even higher. The knowledge of RE ions incorporation in the NCs permits choosing proper doping levels to optimize both linear and nonlinear optical properties. In this work, transparent oxyfluoride glass‐ceramics with LaF3 NCs, doped with Nd 3+ and Er 3+ using oxide and fluoride precursors, were prepared using the melt‐quenching method and controlled crystallization. The local surrounding of the RE ions was studied using X‐ray absorption spectroscopy, electron paramagnetic resonance and photoluminiscence. The results show that most RE ions are already in a fluorine‐rich amorphous environment even in the initial glass. The crystallization process provokes the RE ion redistribution and incorporation in the fluoride NCs. The different RE precursors, used as oxides or fluorides, have an influence on the incorporation of the RE in the NCs and, as a consequence, on the final optical properties.