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In-situ constructing the program-designed nanostructures via laser-direct-writing (LDW) has been proved to be a reliable strategy for optical storage (OS). Herein, it was demonstrated a kind of low-melting Ag+-doped TeO2-ZnO-Na2O (TZN) tellurite glass as ideal LDW OS medium. The microstructural and spectroscopic studies reveal the generation of molecular-like Agmx+ nanoclusters featured with broad emission band in the orange-red region upon laser irradiation. The probe of laser-glass interaction gives evidences on the spatial distribution of Ag species responsive to laser-induced thermoelastic pressure wave oscillation, as well as the heat-driven migration/aggregation of Ag species along the radial direction of laser spot. Raman analyses disclose the loose network of TZN-glass convenient for Ag+ mobility and the increased network connectivity when Agmx+ nanoclusters are precipitated out. Combined with the XPS result of Ag+→Ag0 reduction, the possible formation mechanism of Ag nanoclusters stabilized in glass is proposed. In a proof-of-experiment, the 3D volumetric OS in the TZN glass is demonstrated, showing optical data encoding/decoding in the form of characters and image patterns.

Highly toxic Pb2+ poses a great threat to the health of human beings and ecosystems, urgently calling for an efficient Pb2+ detection method. Herein, we demonstrated a brand-new solid-state fluorescence Pb2+-sensing scheme based on a type of Pb2+-responsive borate glass powder that is able to precipitate CsPbBr3 nanocrystals on the glass surface upon grinding with Pb2+ sources, following a mechanically driven glass crystallization mechanism. Pb2+ sensing is achieved via the Pb2+ concentration-dependent green emission of CsPbBr3 as an indicator signal and independent red emission of Eu3+ as a reference signal. Under UV light irradiation, the obvious emissive color variation from red to green as Pb2+ concentration varies enables the intuitive Pb2+-sensing by naked eyes. With the aid of a spectrometer and smartphone, Pb2+ concentration can be quantitatively determined with the detection limit as low as ∼70 ppm and ∼400 ppm, respectively. The semi-quantitative Pb2+ detection is also possible by comparing the emissive color with the calibrated color card. Hopefully, the proposed solid-state fluorescence Pb2+-sensing strategy with high selectivity can be used for portable and quick Pb2+ analysis in daily life.

With a surface-passivated GaAs, a performance-enhanced, ultrafast, all-optical spatial terahertz modulator was realized. The lower surface recombination rate and longer carrier lifetime induced by passivation render passivated-GaAs superior to pure-GaAs in modulation depth (MD) at a little sacrifice of response rate, eliminating its dependence on intensive laser. At low photodoping levels, the maximum of 1.6-times enhancement in MD was achieved. When the power increased to 60 mW, comparable MD of 94% to that in Si-based one at equivalent photodoping, and simultaneously ultrafast response of 69 MHz which is much faster than 100-kHz level by Si-based, was obtained. This performance-enhanced, ultrafast modulator is highly desired in actual situations and offers a viable avenue to breaking the compromise between MD and speed.

NASICON-type Na3V2(PO4)3 is a promising cathode for sodium-ion batteries owing to its low cost and great thermal stability as well as high energy density, which has attracted ever growing attention. Nevertheless, the pure Na3V2(PO4)3 possesses a bad electrical conductivity, which hinders its Na+-storage performance for energy storage. Designing and fabrication of the phosphorus-doped graphene-decorated Na3V2(PO4)3@C nanocomposite is performed in this research by a simple and rapid method. The constructed network by phosphorus-doped graphene sheet and carbon layer can greatly strengthen the electron and ionic conductivities of Na3V2(PO4)3, leading to outstanding rate capacity together with cyclic property. The as-fabricated electrode shows a specific capacity of 110.6 mAh g−1 at 0.5 C and a high capacity retention of 91.2% over 500 cycles at 20 C. Therefore, this designed nanocomposite is thought as a prospective cathode for batteries that utilize sodium ion as the charge carrier.

In this work, we discovered an unexpected mechanoluminescence (ML) phenomena occurring when transforming amorphous into crystalline, due to the stress-induced precipitation of CsPbBr3 perovskite nanocrystals on glass surface. It is revealed that, unlike the conventional thermal-induced phase transformation mechanism, the breakage of bonding of glass network provides the energy for nucleation and growth, and the shear stress avoids the long-range migration of structural units for crystallization. Such unique ML phenomenon enables the visualization of dynamical force that is inaccessible by common strategy, and so, opens up some novel applications, such as the pressuresensitive “glassy pencil” to learn people’s writing habits, and the Pb2+-detection with good sensitivity and selectivity. These findings not only demonstrate an effective route for the preparation of perovskite materials in a green, time-saving, low cost, and scalable way, enrich the knowledge of glass crystallization mechanism, but also exploit a useful avenue to quantitatively visualize the dynamical force.

Conventional upconversion thermometry strategy, based on the thermally coupled levels (TCL) of lanthanide ions, confronts a dilemma in simultaneously achieving high absolute/relative temperature (T) sensitivities (Sa and Sr) and good signal discriminability. Herein, a novel thermometry strategy by utilizing the synergistic effect of dual-wavelength lasers to manipulate electron thermal distribution is proposed to go beyond the limitation of the TCL-based strategy. In the case of NaGdF4: 20%Yb3+, 2%Er3+ nanoparticles upon 980 & 1530 nm dual-excitation, it is found that more efficient utilization of excited photons results in a higher electron concentration in ladder-like energy levels of Er3+, owing to the diverse pumping routes, which increases transition rate of the T-dependent phonon-assisted cross-relaxation process, and in turn establishes a thermally-sensitive electronic connection between Er3+: 2H11/2,4S3/2 and Er3+: 4F9/2. Remarkably, not only a highest record value of Sa (0.0365 K−1) for the Er3+ doped host materials in the physiological temperature range (303–343 K) is achieved, but also a high Sr (1.29% K-1) and an excellent signal discriminability (Δλ = 112 nm) are obtained. Combining a much intensified upconversion (UC) signal and a good size/shape homogeneity in nanometer scale, the investigated NaGdF4: 20%Yb3+, 2%Er3+ upon dual-wavelength excitation is potentially applicable in the intracellular thermal sensing and imaging. This work exploits an effective way to develop high-performance T-sensors, and the proposed thermometry strategy can be extended to surges of the other lanthanide ions doped systems pumped by multiple-wavelength lasers.

The strong demands for “high-power” w-LEDs stimulate development of the all-inorganic glass ceramic (GC) phosphors with admirable thermal/chemical reliabilities. Herein, an ultra-low melting Sn-P-F-O glass was successfully prepared, demonstrating as an appropriate host to accommodate yellow YAG:Ce3+ and red CASN:Eu2+ without degrading their original luminescent properties. The yellow and red GCs yield QE as high as 92.0% and 88.6%, respectively. Moreover, they exhibit excellent resistance to thermal quenching, i.e., only 9.5% and 3.0% decreases in luminescence intensity at 150 °C compared with that at room temperature. Remarkably, LED using the YAG:Ce3+/CASN:Eu2+ co-sintered GC as color converter yields bright warm white light with CCT of 3554 K, under 350 mA current, highlighting a new record in LE of 90.71 lm/W among the GC-based warm w-LEDs. Accelerated experiments demonstrate the presently studied GC also exhibits a superior thermal stability, therefore is capable for operating at high power condition for a long time.

Compared to the conventional opaque persistent luminescence (PersL) materials, transparent PersL glass and glass ceramic are highly desired for night-vision illumination and indication applications. Herein, we report a new transparent oxyfluoride glass and glass ceramic with multi-color persistent luminescence lasting for ∼1 h visible by the naked eye. By adjusting the crystallization duration, controlled growth of 5–20 nm α-Zn2SiO4 nanocrystals in a glass matrix is achieved. Evidently, the coordination environment of Mn2+ evolves from octahedra in the glass host to tetrahedra in the α-Zn2SiO4 nanophase, resulting in the PersL color changing from red to yellow, and then to green, as the crystallization of Mn2+:α-Zn2SiO4 proceeds. The trap statuses in the glass and glass ceramic are studied in detail aided by EPR and TL measurements, demonstrating that the trapped holes with a trap depth distribution of 0.099–0.789 eV for the glass, and 0.094–0.631 eV for the glass ceramic, determine the PersL behaviors. It is noteworthy that this is the first report that oxyfluoride glass and glass ceramic serve as efficient PersL hosts.

Phosphor-in-glass (PiG) color converter, being regarded as a good encapsulant material for long-lifetime high-powered white light-emitting-diode (LED), has developed rapidly in the recent years. However, it still remains a challenge to achieve fine chromaticity tuning of PiG for high-quality indoor lighting. Herein, a transparent garnet-based PiG was successfully prepared by introducing the Y3Mg2AlSi2O12:Ce3+ orange phosphor and the Y3Al4.6Ga0.4O12:Ce3+ green phosphor into TeO2-based glass matrix. The microstructure and luminescent properties of the PiG were investigated in detail. After optimizing the weight ratio of green phosphor to orange phosphor as well as the PiG thickness, facile chromaticity tuning to follow along Planckian locus in the thus-fabricated LED is achieved; correspondingly the correlated color temperature is adjusted from cool white to warm white. Hopefully, the developed garnet-based PiG is applicable in the long-lifetime color-tunable w-LEDs.

In this work, inorganic perovskite CsPbBr3−xIx (x = 0–3) quantum dots (QDs) were synthesized, and their luminescence properties were studied. The optimized CsPbBrI2 QDs were chosen as red-emitting components to modify Ce3+:YAG-based white LEDs (WLEDs), which exhibit promising performance with a luminous efficacy (LE) of 58 lm W−1, a correlated color temperature (CCT) of 5907 K, and a color rendering index (CRI) of 90, at an operation current of 20 mA. More importantly, optical performance of the CsPbBrI2 QD-modified WLEDs do not exhibit serious degeneration when the operational current increases to as high as 350 mA, being obviously superior to most of the chalcogenide QD-assisted phosphor-converted WLEDs reported previously. These results indicate that the CsPbBr3−xIx QDs are promising red phosphors for high-power WLEDs.

Red-emitting Mn4+ activated oxide phosphors with a cheap price and excellent physical/chemical stability have become a hot research topic for their potential applications in white LEDs (w-LEDs). Herein, we report a novel double-perovskite Gd2ZnTiO6:Mn4+ (GZT:Mn4+) red phosphor. The material microstructures were characterized with the aid of XRD Rietveld refinement and HRTEM observations. The luminescence properties and dynamics of Mn4+ in GZT were studied in detail using low/room temperature steady/transient spectroscopic techniques. The crystal field strength and nephelauxetic effect influencing the Mn4+ emission energy were also analyzed. It is revealed that the special crystal structure of GZT featuring alternately slant-wise arranged [TiO6]/[ZnO6] octahedrons with the [–Mn4+–O2−–Zn2+–] bond angle deviating from 180° is beneficial to achieving efficient Mn4+: 2Eg → 4A2 transition in the deep-red region. After mixing the red-emitting GZT:Mn4+ with the commercial blue and green phosphors in various ratios, and then coupling the mixture with a 365 nm UV chip to build a w-LED, the white light was found to evolve from cool to warm with a tunable correlated color temperature (CCT) from 6977 K to 4742 K, a color rendering index (CRI) up to 82.9, and an improved R9 value to 43, which validates that GZT:Mn4+ is a promising red color converter for UV-based w-LEDs.

Persistent luminescence (PersL) has long commanded the curiosity of researchers owing to the complicated and profound physics behind it. In this work, the PersL mechanism in a new kind of persistent garnet phosphors, Lu2CaMg2(Si1−xGex)3O12:Ce3+, is studied from the new perspective of a “solid-solution” scheme. Different from the conventional study in pursuit of long PersL, we focus on manipulation of afterglow to the millisecond range and tentatively demonstrate its potential to compensate the flickering of the alternating current driven LED (AC-LED) in every AC cycle. Evidently, the tailored host bandgap favors efficient electron charging and facilitates electron detrapping, as well as redeploying trap distribution, which results in a blue light activated afterglow in the millisecond time range, and subsequently a reduced percent flicker of 64.1% for the AC-LED. This investigation is the first attempt to establish the design guidelines for new PersL materials with an adjustable millisecond ranged afterglow, and, hopefully, it paves a pathway to the development of burgeoning low-flickering AC-LED technology.

Eu3+/Ni2+ co-doped transparent glass ceramic containing both hexagonal GdF3 and spinel-like Ga2O3 nano-crystals has been successfully fabricated by melt quenching and subsequent heating. The orderly precipitation of GdF3 and Ga2O3 nano-crystals was discriminated by the X-ray diffraction data and transmission electron microscopy. The incorporation of Eu3+ ions into GdF3 and the selective partitioning of Ni2+ dopants in Ga2O3 were evidenced by the absorption and emission spectra, luminescence decay curves, crystal field calculation, and Judd–Ofelt analysis. Benefitting from the spatial separation, the energy transfer between Eu3+ and Ni2+ was suppressed completely. The distribution related optical properties of Eu3+ and Ni2+ in glass ceramic were investigated in detailed. This work exemplifies a rational design strategy to construct novel multifunctional materials for optical application.

We investigate the tunneling dynamics of a three-dimensional (3D) cigar-shaped dipolar Bose–Einstein condensate (BEC) of 52Cr atoms in an axially-symmetric double-well potential (DWP). By introduci...

All-inorganic cesium lead halide perovskites with high quantum efficiency and narrow emission bandwidth has emerged as a new-generation color converter for wide-color-gamut LCD. Herein, we present the fabrication of this kind of material in a green, time-saving, low cost, and batched way, following the phase transformation from amorphous to crystalline via glass self-crystallization or thermally-/mechanically-driven glass crystallization. A close insight was put into the microstructure-property relationship by making comparison on the samples via different crystallization routes. The CsPbBr3 in glass yields quantum efficiency of ~48% and emission bandwidth of ~30 nm. The color-tunable emission is facilely realized with the introduction of I− species, based on a solid-solution approach. It was demonstrated that the tough issue of poor thermal-/photo-/moisture-stability in perovskites can be well addressed, thanking to the encapsulation of water- and oxygen-impermeable glass matrix. Moreover, a prototype w-LED was fabricated by coupling the CsPbBr3 devitrified glass, the K2SiF6:Mn4+ phosphor-in-glass, with the commercial InGaN blue chip, producing an ultra-wide color gamut of 103.1% NTSC after passing through the commercial RGB color filters.

A novel Sr3La(VO4)3 phosphor is explored which exhibits the bright self-activated luminescence and the ability to sensitize emission of rare earth activators, under the excitation of near UV light. The self-activated emission of the Sr3La(VO4)3 host is peaked at 520 nm with a broad emission band ranging from 400 nm to 700 nm, ascribing to the charge transfer in (VO4)3− groups; while the Sr3La(VO4)3:Eu3+ phosphors show both the broad band luminescence of (VO4)3− groups and the sharp peak emissions of Eu3+ ions. Through doping concentration optimization, intense warm white light is achieved under near UV excitation, with a quantum yield of 31.2%. This phosphor is therefore potentially applicable in near UV chip excited white LEDs.

A blue-emitting phosphor BaSc2Si3O10:Eu(2+) was synthesized using the conventional solid-state reaction. The crystallographic occupancy of Eu(2+) in the BaSc2Si3O10 matrix was studied based on the Rietveld refinement results and the photoluminescence properties. BaSc2Si3O10 exhibits blue emission ascribed to (3)T2-(1)A1 and (3)T1-(1)A1 charge transfer of SiO4(4-) excited by 360 nm. All the phosphors of BaSc2Si3O10:Eu(2+) exhibit strong broad absorption bands in the near ultraviolet range, and give abnormal blue emission upon 330 nm excitation. The abnormal phenomenon was explored in detail through many pieces of experimental evidence. The concentration of Eu(2+) is optimized to be 3 mol% according to emission intensity and the quenching mechanism is verified to be a quadrupole-quadrupole interaction. The CIE coordinates of BaSc2Si3O10:0.03Eu(2+) are calculated to be (0.15, 0.05) and BaSc2Si3O10:0.03Eu(2+) shows similar thermal stability to commercial BaMgAl10O17:Eu(2+).

The commercially dominant phosphor-converted illumination white light-emitting-diodes (w-LEDs) generally suffer from red deficiency and the poor thermal stability of the organic encapsulants, resulting in cool white light, luminous degradation and chromatic aberration for the embedded YAG:Ce3+ phosphors after long-term working. Aiming to solve these problems, herein, a chromaticity-tunable robust phosphor-in-glass (PiG) inorganic color converter was successfully fabricated by co-sintering YAG:Ce3+,Mn2+,Si4+ phosphor particles and the innovatively-designed TeO2–B2O3–ZnO–Na2O–Al2O3 low-melting precursor glass. At first, the spectrally-modified YAG:Ce3+,Mn2+,Si4+ phosphor was prepared by doping Mn2+ as the red emitter and doping Si4+ as the charge compensator through a solid-state reaction route. Then, the YAG:Ce3+,Mn2+,Si4+ powder was incorporated into a specifically prepared precursor glass to form the PiG composite at 550 °C. Owing to the density and the refractive index matches for the phosphor particles and the glass matrix, the particle dispersion in PiG is quite homogeneous and the adverse light-scattering is depressed. The high-power warm w-LED was constructed by coupling a PiG plate with an InGaN blue chip. Remarkably, the chromaticity coordinate of such a w-LED can be well tuned to follow along the Planckian locus with the correlated color temperature evolving from cool white (5541 K) to warm white (3050 K) and a color rendering index around 70, under a driving current of 350 mA. Moreover, the PiG-based warm w-LED presents much superior thermal stability to the traditional phosphor-in-silicone (PiS)-based one. This work highlights the practical applications of the PiG luminescent material in the long-lifetime high-power warm w-LEDs.

The high-powered alternating current (AC) light-emitting diode (LED) (AC-LED), featuring low cost, high energy utilization efficiency, and long service life, will become a new economic growth point in the field of semiconductor lighting. However, flicker of AC-LED in the AC cycles is not healthy for human eyes, and therefore need to be restrained. Herein we report an innovation of persistent "phosphor-in-glass" (PiG) for the remote-type AC-LED, whose afterglow can be efficiently activated by the blue light. It is experimentally demonstrated that the afterglow decay of PiG in the microsecond range can partly compensate the AC time gap. Moreover, the substitution of inorganic glass for organic resins or silicones as the encapsulants would bring out several technological benefits to AC-LED, such as good heat-dissipation, low glare, and excellent physical/chemical stability.

Lanthanide-doped upconversion nanomaterials have attracted great attention recently for their potential applications in the fields of bio-label, three-dimensional display, solar cell and so on. In this article, we report a new strategy to prepare hexagonal Ln 3+ :NaGdF 4 upconversion nanocrystals. Unlike the routine way of synthesizing NaGdF 4 nanocrystals through nucleation and growth, the formation of hexagonal NaGdF 4 nanocrystals herein is realized based on the Ln 3+ -doped cubic CaF 2 precursors, following a hetero-valence cation exchange process between Gd 3+ /Na + and Ca 2+ . Evidently, Ln 3+ dopants in the CaF 2 precursors are retained in the finally formed hexagonal NaGdF 4 nanocrystals and, subsequently, multi-color upconversion emissions are easily realized by simply adjusting the Ln 3+ dopant species and contents in the CaF 2 precursors. This novel hetero-valence cation exchange route may open up a new pathway to synthesize nanomaterials that cannot be fabricated directly.

The phase-separation induced nucleation and growth of Cs 3 LaCl 6 nanocrystals has been studied in the GeS 2 -Ga 2 S 3 -La 2 S 3 -LaCl 3 -CsCl system for the first time. Remarkably, the precipitated chloride nanocrystals are spherical and distributed homogeneously in the glass matrix. Benefiting from the uniform structure, high transparency of the glass ceramic is maintained after heat treatment by reducing adverse optical scattering. As revealed by the absorption spectra and Judd–Ofelt calculations, the doped active rare earth ions are partially partitioned into the low-phonon-energy Cs 3 LaCl 6 nanocrystals, resulting in the decrease of the non-radiative transition probabilities and therefore intensified photoluminescence emission of Nd 3+ and up-conversion one of Er 3+ .

Intense blue-green-emitting Eu2+: Ca3(PO4)2 and tunable multicolor-emitting Eu2+/Mn2+: Ca3(PO4)2 phosphors are prepared via a solid-state reaction route. Eu2+-doped orthorhombic Ca3(PO4)2 phosphor exhibits a broad emission band in the wavelength range of 400–700 nm with a maximum quantum yield of 56.7%, and the emission peak red-shifts gradually from 479 to 520 nm with increase of Eu2+ doping content. Broad excitation spectrum (250–420 nm) of Eu2+: Ca3(PO4)2 matches well with the near-ultraviolet LED chip, indicating its potential applications as tri-color phosphors in white LEDs. Interestingly, Mn2+ co-doping into Eu2+: Ca3(PO4)2 leads to its phase transition from orthorhombic to rhombohedral, and subsequently generates tunable multi-color luminescence from green to red via Eu2+ → Mn2+ energy transfer, under 365 nm UV lamp excitation.

Ni2+/Er3+ dual-doped transparent glass ceramic containing γ-Ga2O3 and β-YF3 nanocrystals is prepared by melt quenching and subsequent heating. It is experimentally demonstrated that Ni2+ and Er3+ are partitioned into γ-Ga2O3 and β-YF3 nanocrystals, respectively, which greatly reduces the adverse energy transfer between them. Accordingly, an integrated broad near-infrared emission band in the wavelength region of 1020–1650 nm, consisting of Ni2+: 3T2(F) → 3A2(F) emission around 1220 nm and Er3+: 4I13/2 → 4I15/2 emission around 1540 nm, is observed under 980 nm excitation. Compared to that in the Ni2+/Er3+ dual-doped glass ceramic containing γ-Ga2O3 and LaF3 nanocrystals, the integrated near-infrared emission intensity in the present sample is increased by two times, ascribing to the higher Er3+ solubility in β-YF3 crystallites.

Tm 3+ -sensitized up-conversion and down-conversion are studied in transparent glass ceramics embedded with β-YF 3 nanocrystals. Upon excitation at 1220 nm, where crystalline silicon (c-Si) solar cells no longer absorb, the sub-bandgap photons could be converted to the higher-energy ones via up-conversion. In addition, under excitation at 468 nm (a wavelength close to the peak in the air-mass 1.5 global solar spectrum), one blue photon might be split in up to two near-infrared ones via down-conversion. In both cases, the frequency-converted photons match the spectral response of c-Si solar cell well. Hopefully, the investigated luminescent materials may act as the spectral conversion layers to reduce the sub-bandgap transmission and charge carrier thermalization losses of c-Si solar cells, and in turn, enhance the energy efficiency.

Nd3+-doped GeS2–In2S3–CsCl transparent chalcohalide glass ceramics containing In2.67S4 nanocrystals are prepared by melt-quenching and subsequent heating. The influence of Nd3+ doping on the In2.67S4 crystallization, the microstructure, as well as the transmission and photoluminescence spectra of glass ceramics are investigated. It is proposed that Nd3+ ions act as nucleating agents for In2.67S4 crystallization in the sample with relative low Nd3+ concentration, while a part of Nd3+ ions are believed being expelled from the crystallized regions and aggregate on the surfaces of the crystallites during crystallization when Nd3+ concentration is increased, which suppresses crystal growth, resulting in nano size and homogeneous distribution of grains, and subsequently remarkable blue-shift of the optical absorption edge of the glass ceramic. Evidently, the microhardness of chalcohalide glass is strengthened after the precipitation of In2.67S4 nanophase.

Highlights: Black-Right-Pointing-Pointer Ultraviolet upconversion emissions of Eu{sup 3+} and Gd{sup 3+} are rarely studied. Black-Right-Pointing-Pointer Nanostructured glass ceramic is developed as a host for ultraviolet upconversion. Black-Right-Pointing-Pointer Ultraviolet upconversion signal are found greatly enhanced after crystallization. Black-Right-Pointing-Pointer It is promising for fabricating novel ultraviolet upconversion lasers. -- Abstract: Ultraviolet multiphoton upconversion emissions of Eu{sup 3+} ({sup 5}H{sub 3-7}, {sup 5}G{sub 2-6}, {sup 5}L{sub 6} {yields} {sup 7}F{sub 0}) and Gd{sup 3+} ({sup 6}I{sub J}, {sup 6}P{sub J} {yields} {sup 8}S{sub 7/2}) are studied in the Eu{sup 3+} (or Gd{sup 3+}) doped SiO{sub 2}-Al{sub 2}O{sub 3}-NaF-YF{sub 3} precursor glasses and glass ceramics containing {beta}-YF{sub 3} nanocrystals, under continuous-wavelength 976 nm laser pumping. It is experimentally demonstrated that energy transfer from Yb{sup 3+} to Tm{sup 3+}, then further to Eu{sup 3+} or Gd{sup 3+} is responsible for the upconversion process. Compared to those in the precursor glasses, the upconversion emission intensities in the glass ceramics are greatly enhanced, owing to the participation of rare earth ions into the low-phonon-energy environment of {beta}-YF{sub 3} nanocrystals. Hopefully, the studied glass ceramics may find potential applications in the field of ultraviolet solid-state lasers.

Transparent SiO 2 –Al 2 O 3 –BaCO 3 –YF 3 –BaF 2 glass ceramics co-doped with Yb 3+ /Ho 3+ ions were prepared by melt quenching and subsequent heating. X-ray diffraction and transmission electron microscopy observation revealed that BaYF 5 nanocrystals incorporated with Yb 3+ and Ho 3+ were precipitated homogeneously among the oxide glass matrix. Three upconversion emission bands centered at 483 nm, 545 nm and 645 nm, corresponding to the 5 F 3 → 5 I 8 , 5 S 2 , 5 F 4 → 5 I 8 and 5 F 5 → 5 I 8 transitions of Ho 3+ respectively, were detected under 976 nm excitation, ascribing to the efficient energy transfer from Yb 3+ to Ho 3+ . The red emission is prevailing in the precursor glass, while the green one turns to be dominant in the glass ceramic.

Eu 3+ -doped transparent nanocomposite of SiO 2 –Al 2 O 3 –NaF–LaF 3 was fabricated by melt-quenching and subsequent heating. X-ray diffraction and transmission electron microscopy analyses evidenced that hexagonal LaF 3 nanocrystals were homogeneously precipitated among the aluminosilicate glass matrix. The distribution of Eu 3+ ions in the nanocomposite was investigated by energy dispersive X-ray spectroscopy, photoluminescence and time-resolved luminescence spectra. The nanocomposite exhibited intense blue and green emissions originating from the 5 D 1,2,3 levels of Eu 3+ incorporated in the low-phonon-energy LaF 3 nanocrystals, and red emission corresponding to the Eu 3+ : 5 D 0 → 7 F J ( J = 0, 1, 2, 3, 4) transitions, under the excitation of single wavelength light at 394 nm. By adjusting the Eu 3+ doping content, various luminescent colors, including perfect white light, were easily tuned through cross relaxation processes between Eu 3+ ions. The results suggest that the Eu 3+ -doped transparent nanocomposite could be potentially applicable as a white-light-emitting material under UV chip excitation.

Rare earth ions-doped transparent glass ceramics containing hexagonal GdF3 nanocrystals with a mean size of 16 nm were prepared. Energy dispersive x-ray spectroscopy and luminescence spectrum investigation evidenced the incorporation of rare earth ions into GdF3 nanocrystals. The efficient energy transfer from Gd3+ to Tb3+ was demonstrated in the Tb3+-doped glass ceramics, which resulted in an intense green light emission originated from Tb3+: 5D4 → 7F6 transition via the sensitization of Gd3+. Compared with the precursor glass, the Dy3+-doped glass ceramic exhibited longer lifetime and lower yellow-to-blue emission intensity ratio owing to the allocation of Dy3+ ions in the low-phonon-energy GdF3 environment. Under ultraviolet excitation, the Dy3+-doped samples emitted bright white light, indicating their potential application in white light emitting diodes.

Er 3+ /Yb 3+ co-doped transparent glass ceramics containing NaYF 4 nanocrystals were prepared by melt-quenching and subsequent heating. Judd–Ofelt analyses of Er 3+ ions in the precursor glasses and glass ceramics were performed to evaluate the intensity parameters Ω 2,4,6 . The Ω 2 value of glass ceramic is smaller than that of glass, which reflects the change of Er 3+ local structure after crystallization, i.e., Er 3+ partitions into the precipitated NaYF 4 nanocrystals. Under 980 nm excitation, intense red and green upconversion luminescence induced by efficient energy transfer from Yb 3+ to Er 3+ was achieved in the glass ceramics. Based on the fluorescence decay lifetimes, the energy transfer efficiency was evaluated, with the maximum value exceeding 68% for the 1 mol% Yb 3+ /2 mol% Er 3+ co-doped sample.

Transparent glass ceramics containing YF 3 nano-crystals were fabricated by heat treatment of the SiO 2 –Al 2 O 3 –NaF–YF 3 –LnF 3 (Ln = Er, Yb) glasses. X-ray diffraction and transmission electron microscopy analyses evidenced the homogeneous distribution of spherical YF 3 nano-crystals sized 25–30 nm among the glassy matrix. Energy dispersive X-ray spectroscopy measurement, combined with the Stark splitting of the absorption and emission bands, verified the incorporation of Er 3+ and Yb 3+ ions into YF 3 nano-crystals. The infrared to visible up-conversion emission of Er 3+ intensified with the increasing of Yb 3+ concentration, ascribing to the increase of the efficiency of non-radiative energy transfer from Yb 3+ to Er 3+ which exceeded 45% for the 0.5Er 3+ /1.0Yb 3+ co-doped sample. The up-conversion luminescence at 545 and 660 nm were affirmed coming from two-photon excitation process.

The 1.53 μm emission of Er 3+ -doped transparent glass ceramics containing NaYF 4 nanocrystals is investigated systematically. The appearance of Stark splits in the absorption and emission peaks of the glass ceramics confirms the incorporation of Er 3+ into NaYF 4 nanocrystals. With the raising of heating temperature for NaYF 4 crystallization, the 4 I 13/2 level lifetime increases due to the incorporation of more Er 3+ into NaYF 4 , while the 1.53 μm emission bandwidth decreases resulting from the structural ordering around Er 3+ . With the increase of Er 3+ content, the obvious concentration quenching effect is observed in glass ceramics. The present glass ceramic possesses large 1.53 μm emission cross-section and high quantum efficiency, which implies that it is potentially applicable in Er 3+ -doped fiber amplifiers.

Er3+:SrF2–SiO2–Al2O3 transparent glass ceramic was prepared by a sol–gel method. The effect of Al3+ doping on the microstructures and luminescence properties of the materials was investigated by the X-ray diffraction (XRD), the transmission electron microscopy (TEM) and the absorption and luminescence spectra measurements. It was evident that Al3+ ions play an important role in improving the structure stability of the glass ceramic by suspending the crystallization of the oxide glassy matrix. The upconversion luminescence of the Al3+-doped glass ceramic was greatly enhanced and visible by the naked eyes, which implies the potential application of this material in the field of solid-state displays.

Transparent glass ceramics containing hexagonal GdF3 nanocrystals were fabricated by melt-quenching and subsequent heating of glass with composition of 44SiO2−28Al2O3−17NaF−11GdF3. The GdF3 nanocrystals with mean size of 6 nm were precipitated during quenching of the melt. Increasing the heating temperature of the quenched sample resulted in the further precipitation and growth of the GdF3 particles. The room temperature photoluminescence spectra of the glass ceramic excited at 398 nm show that, in addition to the characteristic sharp emissions of Eu3+ ions, an intense wide blue emission band ascribing to the Eu2+ 5d → 4f transition also appeared. The obvious Stark splitting of the emissions, the low forced electric dipole 5D0 → 7F2 transition, and the long decay lifetimes of Eu3+ evidenced the partition of Eu3+ ions into the GdF3 nanocrystals, while Eu2+ ions were found to reside in the glass matrix. The excitation and emission spectra demonstrated that the excitation energy of Gd3+ was transferred to bo...

The frequency upconversion emissions of NaYF4 nanocrystals embedded in transparent glass ceramics codoped with Yb3+/Er3+, prepared by melt quenching and subsequent heating, were investigated. It was found that, compared with that of the sample singly doped with 0.5Er3+, the intensities of the green and red upconversion luminescence increased by about 30 and 150 times, respectively, for the sample codoped with 0.5Er3+/1.0Yb3+, attributed to the efficient energy transfer from Yb3+ with high absorption cross section to Er3+ (both of them were concentrated in the NaYF4 nanocrystals). The intense visible upconversion luminescence and the convenient, low-cost synthesis of the glass ceramic make it an excellent substitutional material for the unobtainable bulk NaYF4 crystals potentially applicable in many fields. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Nd 3+ doped transparent oxyfluoride glass ceramic containing β-YF 3 nanocrystals was prepared and the upconversion luminescence behaviors of Nd 3+ in the precursor glass and glass ceramic were investigated. Under 796 nm laser excitation, ultraviolet upconversion emissions of Nd 3+ ions at 354 nm ( 4 D 3/2 → 4 I 9/2 ) and 382 nm ( 4 D 3/2 → 4 I 11/2 ) were observed at room temperature. Power dependence analysis demonstrated that three-photon upconversion processes populated the 4 D 3/2 excited state. In comparison with those of the precursor glass, the ultraviolet emissions were enhanced by a factor of 500 in the glass ceramic, which was attributed to the change in the ligand field of Nd 3+ ions and the decrease in phonon energy because of the partition of Nd 3+ ions into the β-YF 3 nanocrystals after crystallization.

Transparent oxyfluoride glass ceramics doped with different content of Nd3+ were fabricated. X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed abundant spherical NaYF4 nano-crystals distributing homogeneously among the glass matrix. The absorption spectra, emission spectra and F-4(3/2) level fluorescence decay curves of the precursor glasses and glass ceramics were measured. The considerable blue shifts of absorption peaks and longer lifetime of F-4(3/2) level in glass ceramic compared to those in precursor glass indicate the incorporation of Nd3+ into NaYF4 crystallites, which is also confirmed by the Judd-Ofelt calculation. The synchronous variations of the fluorescence lifetime and the quantum efficiency with Nd3+ doping level in glass ceramics indicate the existence of concentration quenching effect, which is considered to originate from the interaction between Nd3+ ions. (c) 2006 Elsevier B.V. All rights reserved.

A complete spectroscopic investigation of energy transfer processes in oxyfluoride glass ceramics containing CaF2 nano-crystals doped with various amounts of Er 3+ and Yb 3+ was reported. An enhancement of the 1.53 lm emission and infrared to visible upconversion fluorescence was confirmed experimentally due to efficient non-radiative energy transfer from Yb 3+ to Er 3+ ions concentrated in CaF2 nano-crystals. The efficiency of Yb 3+ to Er 3+ energy transfer in excess of 85% was obtained for 0.5 mol% Er 3+ /2.0 mol% Yb 3+ co-doped glass ceramic. Using rate equation formulism, the coefficient of Yb 3+ to Er 3+ energy transfer was determined to be about 3.5 times higher than that of Er 3+ to Yb 3+ energy back transfer, which is sufficient to provide high 4 I11/2 population of Er 3+ to improve the fluorescence of the co-doped glass ceramics.

In this paper, the spectroscopic properties of Nd(3+) doped transparent oxyfluoride glass ceramics containing LaF(3) nano-crystals were systematically studied. The formation and distribution of LaF(3) nano-crystals in the glass matrix were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Based on Judd-Ofelt theory, the intensity parameters Omega(t) (t=2, 4, 6), spontaneous emission probability, radiative lifetime, radiative quantum efficiency, width of the emission line and stimulated emission cross-section of Nd(3+) were evaluated. Particularly, the effect of Nd(3+) doping level on them was discussed. With the increase of Nd(3+) concentration in the glass ceramic, the experimental luminescence lifetime, radiative quantum efficiency and stimulated emission cross-section vary from 353.4 micros, 78.3% and 1.86 x 10(-20)cm(2) to 214.7 micros, 39.9% and 1.52 x 10(-20)cm(2), respectively. The comparative study of Nd(3+) spectroscopic parameters in different hosts suggests that the investigated glass ceramic system is potentially applicable as laser materials for 1.06 microm emission.

A new type of glass ceramic containing BaF2 nano-crystals was prepared by melt quenching. Differential scanning calorimetry, X-ray diffraction and transmission electron microscopy were used to study its thermal behaviors and structural characteristics. Based on Judd-Ofelt theory, the spectroscopic properties of the I-4(13)/(2) -> I-4(15/2) transition of Er3+ in glass ceramic were evaluated. Notably, it is found that the fluorescence lifetime in the present system is much longer than that in most other glasses and glass ceramics. A comparative study on luminescence performance suggests that the obtained glass ceramic is a promising material for Er3+ doped fiber amplifiers. (c) 2007 Elsevier B.V. All rights reserved.

The influence of Yb 3+ content on structural evolution and fluorescence properties of oxyfluoride glass ceramics containing LaF 3 nano-crystals were systematically investigated. Differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) experiments indicated that Yb 3+ ions acted as nucleating agent to facilitate LaF 3 crystallization. X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) results verified the incorporation of Yb 3+ into LaF 3 nano-crystal lattice. The absorption, emission spectra and fluorescence decays were measured. The infrared emission intensity of 4 F 5/2 → 4 F 7/2 transition under 980 nm excitation enhanced, while the measured lifetime reduced due to the increase of non-radiative transition probability, with the increase of Yb 3+ content in glass ceramic. However, when Yb 3+ doping reached 4.0 mol% the concentration quenching effect appeared.

SrGa12O19:Cr3+x (x = 0.0005-0.02) are fabricated by calcination of stoichiometric amounts of SrCO3, Ga2O3, and Cr2O3 in air (1.

Er 3+ doped SrF 2 –SiO 2 transparent glass ceramics were prepared by sol–gel method and heat treatment. The decomposition of Sr 2+ –CF 3 COO − and the formation of SrF 2 nano-crystals were found to proceed synchronously in the xerogel. After crystallization of the xerogel, SrF 2 nano-crystals with 8–10 nm in size distributed homogenously among the glassy matrix, and the microstructure of the glass ceramic was stable under and at the temperature of 800 °C probably due to interfacial interaction between nano-crystals and glassy matrix. When heat-treated at 800 °C, the chemically bonded water in the sample was eliminated, resulting in the appearance of the visible luminescence bands of 2 H 11/2 , 4 S 3/2 → 4 I 15/2 and 4 F 9/2 → 4 I 15/2 transitions.

Transparent 45SiO2 25Al2O3 5CaO 10NaF 15CaF2 glass ceramics doped with different levels of Er3+ were prepared. The spherical CaF2 nanocrystals with 10–20 nm in size were verified to be homogeneously embedded among the glassy matrix. Room temperature absorption and emission spectra corresponding to 4I13/2 ↔ 4I15/2 transitions of Er3+ ions in precursor glasses and glass ceramics, respectively had been measured. For glass ceramics, with increasing of Er3+ content from 0.1 to 2.0 mol%, the FWHM values of the emission bands increased from 42 to 71 nm; meanwhile, the lifetime of 4I13/2 level slightly reduced. However, both the values of FWHM and lifetime were larger than those of precursor glasses due to the change of ligand field of Er3+ ions.