Co-doped Oxyfluoride Glass Ceramics Research Articles

Color tunability and temperature sensing capabilities in Dy3+/Sm3+ co-doped transparent oxyfluoride glass ceramics containing K3YF6 nanocrystals

This paper presents the preparation and characterization of transparent oxyfluoride glass ceramics (GCs) that contain nanocrystals of K3YF6 co-doped with Dy3+ and Sm3+. The study investigates the luminescence characteristics, the process of energy transfer (ET) and the behavior of the ratio-metric temperature sensing. The formation of well-defined nanocrystals of K3YF6 in the glass substrate was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). By varying Sm3+ concentration, a tunable emission ranging from pale yellow to orange-red was observed. Energy transfer from Dy3+ to Sm3+ ions was confirmed through fluorescence spectra and decay curves. Sample K3YF6, containing 0.5 mol%Dy3+/1.2 mol%Sm3+, showed an absolute sensitivity (Sa) of 0.635 % K−1 and relative sensitivity (Sr) of 0.401 % K−1. These findings underscore the promising applications of K3YF6: Dy3+, Sm3+ GCs in multicolor displays and high-performance temperature sensing devices.

Effect of microwave heat-treatment on up-conversion luminescence of Er3+/Yb3+ co-doped NaYF4 oxy-fluoride glass-ceramics

The microscopic properties of fluoride grains are known to play critical roles in the up-conversion luminescence properties of phosphors carrying rare-earth-based luminescence centers. To study the effect of different heating methods during preparation on the microstructure and up-conversion luminescence performance of oxy-fluoride glass-ceramics, we synthesized Er3+/Yb3+ co-doped NaYF4 nanocrystals containing transparent glass-ceramics by microwave heat-treatment and the normally heating methods. We characterized the internal structure of glass-ceramics by X-ray diffraction, transmission electron microscopy, mid-infrared spectroscopy, and Raman spectroscopy. While glass-ceramics samples prepared by both methods have extremely high optical transmittance similar to that of a glass, the microwave heat-treatment promoted faster grain growth rate, the glass-ceramics sample had better crystallinity and much improved up-conversion luminescence intensity compared to the sample obtained by the normally heating method.

Effect of rapid thermal annealing treatment on up-conversion luminescence in Er3+/Yb3+ co-doped NaYF4 oxy-fluoride glass-ceramics

The heat-treatment plays a decisive role in the process of crystal phase precipitation and the microscopic features of the fluoride particles, which determines the optical transmittance and up-conversion luminescence (UCL) properties. In this work, we successfully synthesized Er3+/Yb3+ co-doped UCL transparent oxy-fluoride glass-ceramics (GCs) by precipitation of NaYF4 nanoparticles using a rapid thermal annealing (RTA) treatment with ultra-high heating rate (100 K/s). The particle sizes of NaYF4 nanoprecipitation inside glass-ceramic is only 4–5 nm, which is much smaller than the 40–50 nm particle sizes obtained using normal-heating treatment. The GCs with ultra-small particle sizes provided a very high optical transmittance that is close to that of all-amorphous glass, but the intensity of UCL was similar to that of a sample prepared using a slower heating rate. Finally, under different heat treatment conditions the Er3+/Yb3+ co-doped NaYF4 transparent GCs with different particle sizes can be produced, the color and intensity of UCL were controllable.

Effect of glass-ceramics network intermediate Al2O3 content on up-conversion luminescence in Er3+/Yb3+ co-doped NaYF4 oxy-fluoride glass-ceramics

Effect of alumina as a glass network intermediate on the up-conversion luminescence (UCL) in NaYF4:Er3+/Yb3+ co-doped oxy-fluoride glass-ceramics (GCs) was investigated. Combinations of smaller NaYF4 nanocrystals (10 and 13 nm) and lower Al2O3 contents (5% and 10%), as well as larger NaYF4 nanocrystals (26 and 40 nm) and higher lower Al2O3 contents (15% and 20%) were prepared after heat-treatment, respectively. The glass network of intermediate partial replacement of SiO2 with Al2O3 was investigated, and the consequence on the response to the up-conversion of the lanthanide ions was also studied. The UCL properties of Er3+ ions were changed in accordance with the addition of Al2O3, the red UCL intensity decreased with an increased Al2O3 concentration, while the green emission intensity showed opposite tendency. Our results showed that adding Al2O3 to 20 mol% is an effective strategy to simultaneous control of the magnitude and luminescence properties of lanthanide ion doped GCs.

Color-tunable luminescence and temperature sensing in Ce3+/Tb3+ co-doped transparent oxyfluoride glass-ceramics containing Na1.5Y2.5F9 nanocrystals

Transparent glass-ceramics (GCs) containing Na1.5Y2.5F9 nanocrystals doped with Ce3+/Tb3+ were synthesized by melt-quenching approach. The nanocrystal structure was determined by X-ray diffraction, and its distribution and morphology were observed by transmission electron microscope. Luminous characteristics, energy transfer, and temperature sensing performance were investigated. Under 312 nm light excitation, the Ce3+/Tb3+ co-doped Na1.5Y2.5F9 GCs exhibited a blue emission (Ce3+: 424 nm) and sensitized a green emission (Tb3+: 546 nm). The emission color can be adjusted from blue (0.1643, 0.0826) to green (0.2891, 0.5243) via adding Tb3+ ions. The energy transfer efficiencies from Ce3+ to Tb3+ can reach 33.3%. The temperature sensitivity of sample Na1.5Y2.5F9: 0.5Ce3+, 0.1 Tb3+ and sample Na1.5Y2.5F9: 0.5Ce3+, 1.0 Tb3+ were compared. Based on the fluorescence intensity ratio of the Ce3+ and Tb3+ emission, the absolute sensitivity, relative sensitivity, temperature resolution, and thermal repeatability were estimated to be 0.768% K−1, 0.603% K−1, 0.049 K, and 0.993, respectively. The results indicate that Na1.5Y2.5F9: Ce3+, Tb3+ GCs have immense application prospects for multicolor displays and temperature sensors.

Energy transfer and control of color luminescence in Dy3+/Tb3+ co-doped transparent oxyfluorosilicate glass ceramics containing LiYF4 nanocrystals

Dy3+/Tb3+ co-doped oxyfluoride glass ceramics (GC) containing lithium tetrafluoroyttrium (LiYF4) and yttrium fluoride (YF3) nanograins were prepared by a traditional melt-quenching approach. The crystalline phases and morphologies of the GCs were investigated. The GCs showed enhanced green emission from Tb3+ ions and the quenching of Dy3+ emission because of the efficient energy transfer from Dy3+ to Tb3+ ions. The electric dipole-dipole interactions were responsible for the energy transfer mechanism between Dy3+ and Tb3+ ions. The energy transfer efficiencies of these glass ceramics were calculated from their decay curves. The Dy3+/Tb3+ co-doped oxyfluoride GCs with various visible emissions were found to be potential candidates for white-light emitting diode applications.

Upconversion luminescence modulated by alkali metal (Li, Na, and K) induced crystallization in Er3+/Yb3+ co-doped β-PbF2 oxyfluoride glass ceramics

Upconversion luminescence of Er3+/Yb3+ co-doped β-PbF2 oxyfluoride glass ceramics modulated by alkali metals (Li, Na, and K).

Tunable upconversion emission in Er3+/Yb3+ co-doped oxyfluoride glass ceramics containing NaYF4 nanocrystals by the incorporation of Li+ ions

Rare earth doped glass materials with efficient tunable upconversion emission are a challenging field of research in the development of advanced optical devices. In this paper, tunable upconversion emission was realized by incorporating Li+ ions in Er3+/Yb3+ co-doped oxyfluoride glass ceramics containing NaYF4 nanocrystals. The prepared glass ceramics samples experience significant enhancement of luminescence intensity (up to 15 times) under 980 nm excitation. Meanwhile, a composite yellow emission with adjustable CIE chromaticity coordinates was achievable by altering the doping concentration of Li+ ions. The XRD analysis, absorption spectra and Judd-Ofelt theoretical calculations consistently revealed that these phenomena were associated with the Li+ caused shrinkage/expansion of NaYF4 crystal cells, which offers the possibility of emission tuning. The relevant luminescence mechanism was discussed in detail. Furthermore, it may pave new avenue for optimizing novel oxyfluoride glass ceramics applied in various optoelectronic fields.

Visible and Infrared Luminescence, Energy Transfer in Er/Yb Codoped Oxyfluoride Glass Ceramics

Visible and Infrared Luminescence, Energy Transfer in Er/Yb Codoped Oxyfluoride Glass Ceramics

Tailoring up-conversion luminescence for optical thermometry in K+/Er3+ co-doped oxyfluoride glass ceramics

Abstract In this work, a strategy of K+ ions doping was visited with the aim of enhancing up-conversion luminescence (UCL) and sensitivity for optical thermometer of β-PbF2:Er3+ glass ceramics (GCs). Compared to K+-free β-PbF2:Er3+ GCs, the UCL intensity of green (521, 552 nm), red (668 nm), NIR (825 nm) emissions and absolute sensitivity (Sa) for optical thermometer of the β-PbF2:Er3+ GCs co-doped with 10 mol% K+ ions were increased by 176, 82, 18 and 1.5 times, respectively. Charge compensation and the distortion of the local symmetry around the Er3+ ions, when the K+ ions were introduced, were confirmed to be the origin of the enhancement. The results show that K+ ions simultaneous co-doping of β-PbF2:Er3+ glass ceramics (GCs) very effective way to integrate this material for advanced photonic applications.

Energy transfer behaviors and tunable luminescence in Tb3+/Eu3+ codoped oxyfluoride glass ceramics containing cubic/hexagonal NaYF4 nanocrystals

Abstract For glass ceramics, glass crystallization and doping activators into nanocrystalline phases are the key factors determining optical performance, including energy transfer (ET) process. Herein, we propose a strategy to verify ET behaviors based on glass crystallization, elaborately selecting phase-transformed NaYF4: Tb3+, Eu3+ nanocrystals embedded transparent glass ceramics as a typical example. The ET behaviors from Tb3+ to Eu3+ are clarified via photoluminescence spectra, time-resolved spectra and decay curves. Impressively, the corresponding ET process in cubic NaYF4 turns out to be more efficient than that in hexagonal, in spite of a disorder-to-order transformation from cubic to hexagonal. The reason for this abnormal ET efficiency is that dopants prefer to be partitioned into the cubic NaYF4 rather than the hexagonal one during glass crystallization. This work provides keen insights into the relationship between glass crystallization and ET behaviors, which can also feed back to helpfully guide the design and fabrication of glass ceramics with superior optical performance.

Structure and spectroscopic properties of Tb3+/Sm3+ co-doped oxyfluoride glass ceramics containing LiYF4 nanocrystals

In this paper, transparent oxyfluoride glass ceramics containing LiYF4 nanocrystals were successfully synthesized by appropriate heat-treatment on the SiO2-Al2O3-YF3-LiF precursor glass. The average diameter of the LiYF4 nanocrystals is about 16 nm, which has been confirmed by XRD and TEM characterization. Compared with RE3+ (RE = Tb, Sm)-doped glasses, glass ceramics have shown stronger emission intensities due to most rare earth ions have entered LiYF4 nanocrystals with lower phonon energy. A combination of blue, green and orange-red emissions has emerged in Tb3+/Sm3+ co-doped glass ceramics, and white light emission could be realized by varying the proportions of Tb3+ and Sm3+ under UV light excitation. Furthermore, the concentration quenching effect and the Tb3+→Sm3+ energy transfer process were investigated in this paper. Our results indicate that the Tb3+/Sm3+ co-doped oxyfluoride glass-ceramics containing LiYF4 nanocrystals show great potential to achieve a white light emission.

Effect of annealing temperatures on luminescence properties in Ce3+-Yb3+ codoped oxyfluoride glass-ceramics for solar cells

An efficient near-infrared (NIR) down-conversion in Ce3+-Yb3+ codoped oxyfluoride glass ceramics (GC) have been investigated with different annealing temperature. With an 430 nm (Ce3+: 4f → 5d) excitation, the NIR emission at around 1000 nm (Yb3+: 2F5/2 → 2F7/2) was obtained which confirming efficient energy transfer between Ce3+ ions and Yb3+ ions. Subsequently, the possible mechanism of energy transfer was investigated and discussed. Finally, the energy conversion efficiency was measured which the Si solar cell covered by Ce3+-Yb3+ codoped oxyfluoride GC. The maximum efficiency which increased by 0.3% indicated that the Ce3+/Yb3+ sample had the potential applications for solar cells.

Gd3+ doping induced enhanced upconversion luminescence in Er3+/Yb3+ co-doped transparent oxyfluoride glass ceramics containing NaYF4 nanocrystals

In this article, transparent oxyfluoride glass ceramics containing β-NaYF4 nanocrystals were successfully prepared via Gd3+ doping. Compared to conventional non-doped glasses, the thermal treatment temperature required for the precipitation of β-NaYF4 nanocrystals can be lowered with the doping of Gd3+. Furthermore, under the same thermal treatment condition, more β-NaYF4 nanocrystals were precipitated in Gd3+ doped ones, which greatly improves the luminescence efficiency of rare earth doped glass ceramics. Possible mechanism for the Gd3+ doping induced enhanced upconversion luminescence phenomenon was proposed, based on thorough structural and optical characterizations. The results revealed that the doping of Gd3+ ions could decrease the crystallization activation energy and promote the formation of Y-F-Na bonding, which helps the precipitation of β-NaYF4 nanocrystals. Consequently, a large enhancement in upconversion luminescence was achieved. Moreover, the strategy can be successfully applied to the development of other glass ceramic systems for various optoelectronic applications.

Luminescence and energy transfer in Dy3+/Eu3+ co-doped aluminosilicate oxyfluoride glasses and glass-ceramics

A series of oxyfluoride glasses with the composition SiO2–CaF2–Al2O3–CaO, doped with Dy2O3 (0.5–1 mol%) and Eu2O3 (0–4 mol%), have been prepared using the melt quenching method. The glass-ceramics have been obtained by heating the as-made glasses at 680 °C and 750 °C for 1 h. The glasses and the glass-ceramics were investigated using photoluminescence techniques in the near-UV and visible ranges, and differential thermal analysis (DTA) and x-ray diffraction (XRD) measurements were performed. The samples doped with 0.5 mol% Dy3+ were observed to have the highest luminescence intensity under 453 nm excitation compared to the samples doped with 1 mol% Dy3+ and the co-doped samples. The increased luminescence intensity could be caused by energy transfer between rare-earth (RE) ions and cross-relaxation of Dy3+ ions. Energy transfer from Dy3+ to Eu3+ ions in the glasses and the glass-ceramics was confirmed by excitation spectra and luminescence decay kinetics. The average luminescence lifetimes of the Dy3+ emission band at 575 nm under 453 nm excitation decrease with the addition of Eu3+ ions. Energy transfer in the glasses and the glass-ceramics was estimated to be in the range from 11% to 68%, depending on the RE ion concentration.

Wide-range thermometry based on green up-conversion of Yb3+/Er3+ co-doped KLu2F7 transparent bulk oxyfluoride glass ceramics

The development of optical temperature sensors is of fundamental and industrial importance for various applications. Despite the great advance in optical temperature-sensing techniques, challenges remain to search for novel sensing materials with low cost, easy fabrication, high sensitivity and wide temperature-sensing range. Here, bulk KLu2F7:Yb3+/Er3+ glass ceramics (GC), prepared by simple conversional melt-quenching method with subsequent heat-treatment, are carefully characterized for potential temperature sensor using fluorescence intensity ratio (FIR) technique. The structural and luminescent properties of KLu2F7:Yb3+/Er3+ GC are systematically investigated by XRD, TEM, up-conversion and lifetime measurement. Compared to other reported typical Er3+-doped temperature-sensing materials, Er3+ ions in KLu2F7 GC present wide temperature-sensing range (300–773K), large energy gap (861cm−1) and high absolute sensitivity (47.3 × 10−4K−1 at 620K). Our results indicate that KLu2F7:Yb3+/Er3+ GC are promising temperature sensing materials for designing highly sensitive FIR-based optical thermometers.

Effects of crystal structure transformation on cooperative up-conversion luminescence in the Tb3+-Yb3+ co-doped oxyfluoride glass-ceramics

In this study, Tb3+-Yb3+ co-doped transparent oxyfluoride glass-ceramics were prepared respectively from melt-quenched glass samples with the molar compositions of 45SiO2-15Al2O3-12Na2CO3-21BaF2-(7-x)LaF3-xYF3 (x = 0, 1, 3, 6 and 7). It was found that the crystal structure of the annealed glass-ceramics strongly depended on the ratio of YF3/LaF3. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results revealed that the crystal structure transformed from cubic Ba2LaF7 phase to cubic intermediate phase and finally to cubic BaYF5 phase, the BaYF5 nanocrystal was determined as cubic structure instead of the reported tetragonal structure for the first time via a Rietveld refinement method with TOPAS. In the process of crystal structure transformation, the local symmetry around Tb3+ ions was infected by different types of irregularly arranged interstitial F- ions, which further affected the effective phonon energy around Tb3+ ions. The high effective phonon energy around Tb3+ ions in the intermediate phase could strongly enhance the up-conversion (UC) luminescence intensity, and thus improved the UC luminescence efficiency.

Adjustable multicolor up-energy conversion in light-luminesce in Tb3+/Tm3+/Yb3+ co-doped oxyfluorifFde glass-ceramics containing Ba2LaF7 nanocrystals

Transparent oxyfluoride glasses with highly efficient up-energy conversion (UEC) luminescence were developed in the 45SiO2-15Al2O3-12Na2CO3-21BaF2-7LaF3-xTbF3-yTmF3-zYbF3 composition (in mol%), and structural investigation by X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the formation of face-centered cubic Ba2LaF7 nanocrystals. The colors of UEC luminescences could be tuned easily by adjusting the concentration of doped rare earth ions and the excitation power of laser simultaneously. The relationship between the emission intensity of Tb3+/Tm3+/Yb3+ co-doped oxyfluoride glass-ceramics and the excitation pump power revealed that three-photon and two-photon absorptions predominated in the conversion process from the infrared into blue and red luminescences, respectively. A novel UEC mechanism of red emission from Tm3+ was proposed, energy transfers from Yb3+ to Tm3+ and Tb3+ and from Tm3+ to Tb3+ were evidenced. The possible mechanism responsible for the color variation of UEC in Tb3+/Tm3+/Yb3+ co-doped was discussed.

Effect of lithium halide on glass network structure and upconversion luminescence in Er3+ co-doped oxyfluoride glass ceramics containing NaGdF4 nanocrystals

LiR(R = Br, Cl, F) co-doped oxyfluoride glass ceramics containing NaGdF4 nanocrystals were prepared. The effect on glass network structure by dopants was investigated through the Raman spectra. The crystallization temperature and integrity of the glass network structure was gradually reduced by introducing halogen ions. The types and distribution of nanocrystals were determined by X-ray diffraction and transmission electron microscope. The size of nanocrystals were shown in column type distribution map. The mean size of nanocrystals was bigger from SABr to SAF. The upconversion luminescence of Er3+ in SABr, SACl and SAF were study. The intensity ratio of red and green light was reduced in glass ceramics when the content from LiBr turn to LiF.

Intense ∼1.2 μm emission from Ho3+/Y3+ ions co-doped oxyfluoride glass-ceramics containing BaF2 nanocrystals

Ho3+/Y3+ co-doped BaF2 nanocrystals were precipitated in oxyfluoride glasses through conventional melt-quenching and subsequent thermal treatment. X-ray diffraction patterns, transmission electron microscope images and absorption spectra confirmed the incorporation of Ho3+/Y3+ ions into BaF2 nanocrystals in glass-ceramics. With the gradual substitution of Ho3+ ions by Y3+ ions, concentration dependent energy transfer between excited Ho3+ ions were suppressed and relative emission intensity at 1.2 μm band was enhanced. The maximum emission cross-section calculated was 0.60 × 10−20 cm2 in BH1-GC specimen, indicating that Ho3+/Y3+ co-doped glass-ceramics have a great potential for the development of 1.2 μm band gain medium.