Investigation on Crystallization and Optical Properties of Ca_1−xLa_xF_2+x Glass‐Ceramics

Abstract

Transparent oxyfluoride glass‐ceramics containing Er3+, Yb3+:Ca1−xLaxF2+x nanocrystals, which may have potential applications in the fields of solid‐state laser and luminescence, were prepared. Crystallization of Ca1−xLaxF2+x and behavior of Yb3+ and Er3+ during the heat treatment was investigated. Results showed that alumina content had a significant effect on crystallization of Ca1−xLaxF2+x in the SiO2–Al2O3–CaF2–LaF3 system. Due to the size of phase‐separated areas, the size of the crystals during the heat treatment did not change significantly. After crystallization of Ca1−xLaxF2+x in the glass, the majority of Er3+ ions incorporated into the Ca1−xLaxF2+x crystals during the heat‐treatment process. Time‐resolved luminescence of Er3+ ions in the samples around 842 nm showed that the solubility of Er3+ ions in Ca1−xLaxF3 crystals is higher than pure CaF2 crystals. The glass undergoes an enormous phase separation, which keeps the Yb3+ ions within the other separated phase. Therefore, only at high temperatures (790°C) or with a long heat‐treatment time (72 h), there is a possibility for Yb3+ ions to be incorporated into the fluorine phase.

Transparent oxyfluoride glass ceramics

“…Calculation of the actual parameters for the crystal lattices and their comparison with the literature data with the use of known a(x) concentration dependencies could be of great help, but most authors don't even attempt to index their X-ray diffraction patterns. Description of Сa 1-x La x F 2+x solid solution in [68] represents a rare exception to that trend.…”

“…Thus, Sontakke and Annapurna [172] studied energy transfer kinetics for combinations of different donor-acceptor ions (e.g., Nd 3+ /Yb 3+ ; Yb 3+ /Dy 3+ ; Nd 3+ /Dy 3+ ) in cubic NaYF 4 nanoparticles; Lin et al [150] and Yu et al [95] studied Tm 3+ ions up-and down-conversion luminescence; and Wang and Ohwaki [19] were the first ones who achieved an up-conversion luminescence for Yb 3+ /Er 3+ ionic pair in fluoride glass ceramics (Pb 1-x Cd x F 2 -based nanoparticles) with energy transformation from the nearinfrared to the visible part of the spectrum. Later, the same activator couple was used in nanoparticles of different chemical compositions, such as PbF 2 [53,115,193], "Pb 4 Yb 3 F 17 " [23], CaF 2 [74,86,89,330], Ca 1-x La x F 2+x [68], SrF 2 [142], BaF 2 [230], "Ba 2 GdF 7 " [42,200], NaYF 4 [44], YOF [204], β-NaCaAlF 6 [96] and other [58] surrounded by oxide glass matrixes. The up-conversion luminescence for Yb 3+ /Tm 3+ ion pair in oxifluoride glass ceramics has been studied for PbF 2 [117,222], SrF 2 [138], "Ba 2 GdF 7 " [199], β-YF 3 [190] nanocrystals.…”

Thermal and crystallization behavior of SiO2‐PbF2 glass system in the presence of ErF3 and Al2O3

“…The liquid‐liquid phase separation by nucleation and growth mechanism is required for narrow crystal size distribution. The fluorine‐rich phase‐separated liquid droplets play key role as the nucleation centers, and provide semi isolated regions as template for fluoride crystallization in the glass matrix …”

“…Several decades have passed from introduction of upconversion phenomenon as an anti‐Stokes process and rare‐earth‐doped oxyfluoride glass‐ceramics in 1970s by Auzel . Upconversion materials have recently attracted great attentions due to their specific optical features in various fields such as telecommunication windows, biological applications, efficient photovoltaic solar cells, and high capacity data storage optical devices . Rare‐earth ions are the most utilitarian elements in these areas, and special characteristics of oxyfluoride glass‐ceramics make them the most interesting hosts for rare‐earth ions in optical applications.…”

Preparation and optical properties of Eu 3+ doped and Er 3+ /Yb 3+ codoped oxyfluoride glass ceramics containing Ba 1−x Lu x F 2+x nanocrystals

“…In the oxyfluoride glass ceramics, BaF 2 could be easily precipitated from the precursor glass and strong fluorescence emission of RE ions in the oxyfluoride glass ceramics was obtained [13]. However, the influence of LnF 3 on the crystallization mechanism of BaF 2 nanocrystals and optical properties of RE ions in the glass ceramics was scarcely investigated [14,15].…”