Transparent Oxyfluoride Glass Ceramics Research Articles

Luminescence properties of Pr3+-doped transparent oxyfluoride glass–ceramics containing BaYF5 nanocrystals

Transparent oxyfluoride glass–ceramics containing BaYF5 nanocrystals were successfully synthesized by appropriate heat-treatment on the SiO2–Al2O3–Na2O–BaF2–Y2O3–Pr6O11 precursor glass. The structure and luminescence properties of the precursor glass and glass–ceramics were investigated by DSC, XRD, TEM, optical transmission, photoluminescence, decay time and radioluminescence spectra. The XRD results indicate that the BaYF5 nanocrystals can percitated in the precursor glass and the sharper emission peaks of Pr3+ in glass ceramic suggests that Pr3+ ions are incorporated into the BaYF5 nanocrystals. The higher the heat-treatment temperature is, the more the Pr3+ ions are centered into BaYF5 nanocrystals, which results in the optimal concentration of Pr3+ in glass ceramic changes on heat-treatment temperature. It is notable that the emission intensity of both photoluminescence and radioluminescence for 0.1mol% Pr3+ in the glass ceramic (GC665) are stronger than those in the precursor glass. The mechanism of enhanced luminescence is also discussed.

Efficient down- and up-conversion of Pr 3+–Yb 3+ co-doped transparent oxyfluoride glass ceramics

Pr 3+ and/or Yb 3+ doped transparent oxyfluoride glass ceramics (GCs) containing CaF 2 nanocrystals were fabricated and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Judd–Ofelt (J–O) intensity parameters, radiative transition probability, radiative lifetimes, and branching ratios of Pr 3+ have been calculated from the absorption spectra. Upon 470 nm excitation, Pr 3+ doped GCs yield intense visible-near infrared (NIR) luminescence corresponding to the 3P 0 → 3H 6, 3P 0 → 3F 2,3,4, 3P 1 → 1G 4, 1D 2 → 3H 5, and 1D 2 → 3F 4 transitions, respectively. With the addition of Yb 3+ ions, NIR down-conversion (DC) emissions at 976 nm ( 2F 5/2 → 2F 7/2) were achieved, due to efficient energy transfer (ET) from Pr 3+ to Yb 3+. Underlying mechanism for the NIR-DC is analyzed in terms of static and dynamic photoemission and monitored excitation spectra. The maximum quantum efficiency from Pr 3+: 3P 0 to Yb 3+: 2F 5/2 is calculated to be 153%. In comparison, intense up-conversion emissions at 489, 545, 606, and 651 nm have been obtained in Pr 3+–Yb 3+ codoped glass and GCs under 980 nm excitation, which is ascribed to be two-photon involved ET from Yb 3+ to Pr 3+.

Enhanced luminescent properties of Tb3+ ions in transparent glass ceramics containing BaGdF5 nanocrystals

Tb3+ doped transparent oxyfluoride glass ceramics containing BaGdF5 nanocrystals were prepared. The transmission spectra, photoluminescence spectra, decay time and X-ray excited luminescence spectra of the Tb3+-doped glass and glass ceramics were investigated. Energy transfer from Gd3+ to Tb3+ has been observed in the glass and glass ceramics. The emission intensity of green band (5D4→7FJ) of the Tb3+-doped glass ceramics is enhanced compared with that of the glass under ultraviolet and X-rays, which could be attributed to that the generation of BaGdF5 nanocrystals with low phonon energy reduces the non-radiative transitions.

The microstructure of erbium–ytterbium co-doped oxyfluoride glass–ceramic optical fibers

Oxyfluoride transparent glass–ceramics combine some features of glasses (easier shaping or lower than single crystals cost of fabrication) and some advantages of rare-earth doped single crystals (narrow absorption/emission lines and longer lifetimes of luminescent levels). Since the material seems to be promising candidate for efficient fiber amplifiers, the manufacturing as well as structural and optical examination of the oxyfluoride glass–ceramic fibers doped with rare-earth ions seems to be a serious challenge. In the first stage oxyfluoride glasses of the following compositions 48SiO2–11Al2O3–7Na2CO3–10CaO–10PbO–11PbF2–3ErF3 and 48SiO2–11Al2O3–7Na2CO3–10CaO–10PbO–10PbF2–3YbF3–1ErF3 (in molar%) were fabricated from high purity commercial chemicals (Sigma–Aldrich). The fabricated glass preforms were drawn into glass fibers using the mini-tower. Finally, the transparent Er3+ doped and Er3+/Yb3+ co-doped oxyfluoride glass–ceramic fibers were obtained by controlled heat treatment of glass fibers. The preceding differential thermal analysis (DTA) studies allowed estimating both the fiber drawing temperature and the controlled crystallization temperature of glass fibers. X-ray diffraction examination (XRD) at each stage of the glass–ceramic fibers fabrication confirmed the undesirable crystallization of preforms and glass fibers has been avoided. The fibers shown their mixed amorphous–crystalline microstructure with nano-crystals of size even below 10nm distributed in the glassy host. The crystal structure of the grown nano-crystals has been determined by XRD and confirmed by electron diffraction (SAED). Results obtained by both techniques seem to be compatible: Er3FO10Si3 (monoclinic; ICSD 92512), Pb5Al3F19 (triclinic; ICSD 91325) and Er4F2O11Si3 (triclinic; ICSD 51510) against to initially expected PbF2 crystals.

Influence of temperature on the fluorescence intensity of Tm<sup>3+</sup> doped in oxyfluoride glass ceramics

The sample of transparent oxyfluoride glass ceramics was excited by a red pulsed laser which had a tunable wavelength between 602 and 660 nm. The fluorescence intensities of Tm3+ ion under different temperatures were measured, and the relationship between them was also recorded. It was shown that the upconversion emission at 454 nm was very strong at 100–200 K under the excitation at 643.2 nm. The upconversion intensity increased initially and then decreased with the decrease of temperature, and the fluorescence intensities increased with the decrease of temperature under the excitations at 656.0 and 638.0 nm. Additionally, the efficiencies of the upconversion under 643.2 and 638.0 nm excitations exceeded that of 656.0 nm, which suggested us that it was easy to complete the upconversion when the excitation wavelength was resonant with the excited state absorption, and a proper theoretical explanation was proposed based on the upconversion mechanism of Tm3+, phonon energy, and so on.

Transparent oxyfluoride glass ceramics co-doped with Er 3+ and Yb 3+ – Crystallization and upconversion spectroscopy

Transparent glass ceramics in the system SiO 2–B 2O 3–PbO–CdO–PbF 2–CdF 2–YbF 3–ErF 3 showing infrared to visible anti-Stokes (upconversion) luminescence are studied in the present work. The glass compositions have been optimized in order to reduce the melting temperature and, hence, to obtain laboratory scale samples with good optical quality. Erbium-doped nanoscale Pb 4Yb 3F 17 crystals are precipitated in the precursor glasses during annealing at temperatures 30–40 K above T g . A kinetically self-constrained growth explains the nano sizes of the crystals. Both the Stokes and anti-Stokes luminescence spectra of glasses could be explained with clustering of the Yb 3+ and Er 3+ ions in fluorine-rich regions. At the annealing temperature these regions act as nucleation precursors. The crystal growth further enhances the local concentration of these ions. Consequently, a series of energy transfer and energy cross relaxation processes occurs between adjacent rare earth ions leading to the observed luminescence spectra of the glass ceramics studied.

Enhanced mid-IR emission in Yb 3+–Tm 3+ co-doped oxyfluoride glass ceramics

Tm 3+–Yb 3+ co-doped transparent oxyfluoride glass ceramics were prepared through thermal treatment of the as-prepared glasses. The precipitation of nanocrystals and the incorporation of Tm 3+ and Yb 3+ into the nanocrystals were confirmed by X-ray diffraction and absorption spectra. Based on the Judd–Ofelt theory, the J–O parameters Ω λ ( λ = 2, 4, 6), spontaneous radiative transition rates, radiative lifetimes and fluorescence branching ratios of Tm 3+ in both as-prepared glasses and glass ceramics were calculated. Intense mid-IR emission and upconversion luminescence in the Tm 3+ and Yb 3+ co-doped glass ceramics were observed under 980 nm excitation. Especially, compared with that of the as-prepared glasses, mid-IR luminescence intensity of Tm 3+ in the glass ceramics was greatly enhanced. Desirable spectroscopic characteristics suggest that these oxyfluoride glass ceramics may be promising mid-IR laser active medium.

Tm 3+ doped oxy-fluoride glass-ceramics containing NaLaF 4 nano-crystals

Oxy-fluoride glass-ceramics offer a promising alternative as hosting of lanthanide ions, making them suitable for the fabrication of optical devices. In this study, transparent oxy-fluoride glass-ceramics doped with Tm 3+ have been obtained from glasses in the system K 2O–Na 2O–Al 2O 3–SiO 2–LaF 3 by heat treatments slightly above the glass transition temperature, T g. Under that treatment, NaLaF 4 nano-crystals with sizes up to 30 nm precipitate. The crystallisation has been studied as a function of the heat treatment by using dilatometry, X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. The distribution of Tm 3+ between glassy matrix and fluoride nano-crystals has been analysed from photoluminescence spectra.

2.0 μm Emission properties of transparent oxyfluoride glass ceramics doped with Yb 3+–Ho 3+ ions

Transparent oxyfluoride glass and glass ceramics doped with 3.0 mol% Yb 3+ and 0.5 mol% Ho 3+ ions have been prepared. The investigated samples show efficient 2.0 μm emission. The absorption and emission cross sections corresponding to the 5I 7– 5I 8 transitions of Ho 3+ (at 2.0 μm) have been calculated according to the McCumber theory. Glass sample heat-treated at 470 °C has the maximum absorption and emission cross sections of 5.58 × 10 −21 cm 2 at 1949 nm and 6.64 × 10 −21 cm 2 at 2034 nm. The Yb 3+–Ho 3+ doped oxyfluoride glass ceramic exhibits an advantage for application in 2.0 μm laser devices.

Tunable green-red luminescence in Ho 3+/Yb 3+/Ce 3+: YF 3 nanocrystals embedded transparent glass ceramics

The Ho 3+/Yb 3+/Ce 3+:YF 3 nanocrystals embedded transparent oxyfluoride glass ceramics were successfully synthesized and the emission spectra have been measured. We changed the doped concentrations of ion Ce 3+ in the glass ceramics and unexpectedly found that the different concentrations brought forth different luminescence wavelengths, a tunable luminescence wave band from green to red, which might be useful to the tunable visible laser or display applications. In addition, excitated with wavelength 975 nm LD, the transitions of Ho 3+: 5G 4 → 5I 8 at 390 nm, 5G 5 → 5I 8 at 420 nm and 5F 3 → 5I 8 at wavelength 490 nm were observed in the glass ceramic GCCe0, while in samples GCCeJ(J=1,3,5,8), the three peaks disappeared.

Infrared-to-visible conversion luminescence of Er 3+ ions in lead borate transparent glass-ceramics

Transparent glass-ceramics were successfully prepared during controlled heat treatment of lead borate glasses. The PbF 2 particles were dispersed into a borate glass matrix which was evidenced by X-ray diffraction analysis. The phase identification revealed that crystalline peaks can be related to the orthorhombic PbF 2 phase. Green up-conversion luminescence due to the 4S 3/2– 4I 15/2 transition of Er 3+ ions was registered. In comparison to the precursor glass the luminescence intensity was considerably higher, whereas the luminescence linewidth slightly decreased in the studied oxyfluoride transparent glass-ceramics. It indicated that a part of the trivalent erbium was incorporated into the PbF 2 crystalline phase.

Measurement of Quantum Yield of Up-Conversion Luminescence in Er<SUP>3+</SUP>-Doped Nano-Glass-Ceramics

A measurement of quantum yield of up-conversion luminescence has been done for the Er(3+)-doped transparent oxyfluoride glass-ceramics 32(SiO,)9(AlO1.5)31.5(CdF2)18.5(PbF2)5.5(ZnF2): 3.5(ErF3) mol%, where most of Er3+ dopants partition in 8 nm diameter nano-crystals Er10Pb25F65. The yield was found by newly proposed method using the pump power dependence of the resonant luminescence. The result of the measurement points out that a theoretical maximum of 50% may be reached for the up-conversion luminescence yield in this material. This high yield is shown to be due to low phonon energy and short inter-dopant distances in the nano-crystals.

新型铒镱共掺杂氧氟硼硅酸盐微晶玻璃上转换发光的研究

The upconversion luminescence of Er3+/Yb3+ ions is researched in a novel transparent oxyfluoride borosilicate glass and glass ceramics under 980-nm excitation. Fluoride nanocrystals Ba2YF7 are successfully precipitated in glass matrix, which is affirmed by the X-ray diffraction results. Compared with the parent glasses, significant enhancement of upconversion luminescence is observed in the Er3+/Yb3+ codoped transparent glass-ceramics, which may be due to the variation of coordination environment around Er3+ and Yb3+ ions after crystallization. The possible upconversion mechanism is also discussed.

Pr3+-Yb3+共添加オキシフロライド透明結晶化ガラスにおける量子切断と１μm発光

Pr3+-Yb3+共添加オキシフロライド透明結晶化ガラスにおける量子切断と１μm発光

Fluorescence characteristics of Tm3+ in different local environments

Fluorescence from ions in both the crystal and glass phases was investigated by selective excitation of Tm3+ doped transparent oxyfluoride glass ceramics containing LaF3 nanocrystals. The spectroscopic properties of ions in different local environments were studied. It was found that the glass phase favored blue up-conversion of Tm3+ when a pulsed red light was applied. The most efficient up-conversion was obtained when the excited state absorption was resonant with the excitation.

Enhanced cooperative quantum cutting in Tm^3+- Yb^3+ codoped glass ceramics containing LaF_3 nanocrystals

Tm(3+)-Yb(3+) codoped transparent oxyfluoride glass ceramics containing LaF(3) nanocrystals were obtained by thermal treatment on the as-made glasses. The formation of LaF(3) nanocrystals and the incorporation of Tm(3+) and Yb(3+) into LaF(3) nanocrystal lattice were confirmed by X-ray diffraction and high resolution transmission electron microscopy. Infrared quantum cutting involving Yb(3+) 950-1100 nm ((2)F(5/2)--> (2)F(7/2)) emission was achieved upon the excitation of the (1)G(4) energy level of Tm(3+) at 468 nm. We measured the photoluminescence properties of these glass ceramics. We also investigated the thermal treatment duration dependent quantum efficiency, and found that the quantum efficiency is 13% increased for the 0.5Tm(3+)-4Yb(3+) doped glass ceramic with a maximum value of 144%, and 16% increased for the 0.5Tm3+-8Yb3+ doped glass ceramic with a maximum value of 162%, respectively.

The effect of PbF 2 content on the microstructure and upconversion luminescence of Er 3+-doped SiO 2–PbF 2–PbO glass ceramics

The Er 3+ doped transparent oxyfluoride glass ceramics were obtained by appropriate heat treatment of the precursor glasses with composition (mol%) 50SiO 2– xPbF 2–(50 − x)PbO–0.5ErF 3. The microstructure and optical properties of the glasses and glass ceramics were determined by differential scanning calorimetry (DSC), X-ray diffraction (XRD), absorption spectra and luminescence spectra. The intensity of upconversion luminescence significantly increased in glass ceramics compared to that in precursor glass. The emission bands centered around 660 nm ( 4F 9/2 → 4I 15/2) and 410 nm ( 2H 9/2 → 4I 15/2) were simultaneously observed in glass ceramics but cannot be seen in the corresponding precursor glass. The influence of different PbF 2 content on the microstructure and upconversion luminescence of the samples was analyzed in detail. The results indicated that with the increase of PbF 2 content, the Ω 2 was almost the same and the ratios of red to green upconversion luminescence decreased in glass ceramics.

Infrared quantum cutting in Tb3+,Yb3+ codoped transparent glass ceramics containing CaF2 nanocrystals

Tb 3 + – Yb 3 + codoped transparent oxyfluoride glass ceramics containing CaF2 nanocrystals were synthesized. The formation of CaF2 nanocrystals in the glass ceramics was confirmed by x-ray diffraction and high resolution transmission electron microscopy. The incorporation of Tb3+ and Yb3+ into CaF2 nanocrystal lattice was confirmed by energy dispersive spectroscopy. Infrared quantum cutting involving Yb3+ 950–1100nm (F5∕22→F7∕22) emission was achieved upon the excitation of D45 energy level of Tb3+ at 484nm. The photoluminescence properties have been studied for these glass ceramics. Yb3+ concentration dependent quantum efficiency was calculated, and the maximum efficiency approaches 155% before reaching concentration quenching threshold.

Optical Dephasing of Triply Ionized Rare Earths in Transparent Glass Ceramics Containing LaF3 Nanocrystals

Optical dephasing of Pr3+ and Tm3+ ions doped in transparent oxyfluoride glass ceramics was studied with the two-pulse photon echo technique. It was found that the dephasing time of rare earth ions is dramatically less in nanocrystals embedded in a glass matrix than in bulk crystals. A quasi-linear temperature dependence obtained at low temperatures proved that the long-range interaction of the ions inside the nanocrystals with the two level systems of the glass matrix dominates the optical dephasing. The local thermal effect in glass ceramics containing nanocrystals elevates the local temperature, which results in the reduction of optical dephasing time. For Tm(3+)-doped glass ceramics, the elevation of local temperature induced by the irradiation of excitation laser even quenched the photon echo signals in the experimental study.

Spectroscopic study of local thermal effect in transparent glass ceramics containing nanoparticles

Local thermal effect influencing the fluorescence of triply ionized rare earth ions doped in nanocrystals is studied with laser spectroscopy and theory of thermal transportation for transparent oxyfluoride glass ceramics containing nanocrystals. The result shows that the local temperature of the nanocrystals embedded in glass matrices is much higher than the environmental temperature of the sample. It is suggested that the temperature-dependent thermal energy induced by the light absorption must be considered when the theory of thermal transportation is applied to the study of local thermal effect.