Phosphate Glass-ceramics Research Articles

Research Progress of Immobilization of High-Level Nuclear Waste by Using Phosphate Glass-Ceramics

Research Progress of Immobilization of High-Level Nuclear Waste by Using Phosphate Glass-Ceramics

Luminescence and energy transfer of color-tunable Tb3+/Sm3+co-doped BaZn2(PO4)2 glass-ceramic phosphors

The color-tunable phosphors can be obtained by co-doping strategy and energy transfer regulation. In this work, Tb3+ and Sm3+ co-doped BaZn2(PO4)2 glass-ceramic (GC) phosphors are prepared and their structural, optical and luminescent properties are characterized. By adjusting the doping concentration of Sm3+, The luminescent color of BaZn2(PO4)2 GC: Tb3+/Sm3+ Phosphors ranges from green to light green to yellow-green and finally to yellow. The photoluminescence (PL) spectra and fluorescence decay curves confirmed the energy transfer from Tb3+ to Sm3+, and the energy transfer efficiency (η) increased monotonically with the increase of Sm3+ concentration. Moreover, the energy transfer mechanism from Tb3+ to Sm3+ in BaZn2(PO4)2 GC is a dipole-dipole interaction. The typical BaZn2(PO4)2 GC: 0.75 Tb3+/0.75Sm3+ phosphor has a high thermal stability with an activation energy determined to be 0.29525 eV. Coupling BaZn2(PO4)2 GC: 0.75 Tb3+/0.75Sm3+ Phosphors with commercially available ultraviolet light-emitting diodes (UV-LEDs) chips yields luminescent color coordinates of (0.3965, 0.4253) and a color correlation temperature of 3927 K, close to warm white light emission. These results indicated that the Tb3+ and Sm3+ co-doped BaZn2(PO4)2 GC achieved luminescence color modulation, which has potential applications in UV-converted LEDs and other optical devices.

Luminescence investigations on Dy3+ doped CdO-PbF2 phosphate glass-ceramics

• P 2 O 5 – CdO – PbF 2 -SrO – Dy 2 O 3 glass and the corresponding glass-ceramics were prepared. • Existence of PbF 2 crystallites and their structural confirmations were done by X-ray diffraction studies. • Effect of heat treatment on luminescence was discussed. • Decrease in luminescence intensity in presence of nanocrystals in glass ceramics was reported This paper reports the structural and photoluminescence investigations on Dy 3+ doped transparent CdO-PbF 2 phosphate glass/glass ceramics with SrO. Upon heat treatment, the nanocrystals occurred in glass ceramics are spherical in shape in the sizes of 10nm to 20nm. The luminescence intensities were strongly dependent on nanocrystallinity and showing the same kinetics as efficient luminescent hosts. In the present host, well incorporation of Dy 3+ ions in nanocrystals and low energy transfer to Dy 3+ ions due to existence of other crystalline phases, both the mechanisms occurred. The consequent variations in luminescence intensities also observed.

Long afterglow from multi dopant transparent and opaque glass ceramic phosphor for white, red, yellow, and blue emissions: Zn2SiO4:Eu3+, Dy3+, Mn2+

In this paper, preparation of long afterglow phosphor with different emission colors in the system Zn2SiO4:Eu3+, Dy3+, Mn2+ was done via melt-quenching technique. The effect of adding mono-di- and tri-dopant on the phosphorescence properties was studied. Also, the effect of applying different heat treatment programs on the appearance of glass-ceramic (GC) to get transparent or opaque materials were optimized. DTA, XRD, SEM, UV–visible - NIR, and fluorescence spectrophotometer were used to characterize the obtained materials. The results revealed crystallization of willemite and zinc borate; both Mn and Dy addition enhanced the degree of crystallization while Eu depressed it. Heat treatment at 650 °C/5 h revealed transparent glass-ceramic (TGC), above this temperature opaque glass-ceramic was appeared. Calculation of optical band gap (Eopt), Urbagh energy (∆E) and refractive index were located in the range: 2.1–2.8 eV, 0.53–0.79 eV and 2.45–2.64 respectively. Lifetime decay was increased by increasing heat treatment temperature; it reaches ~2 h after irradiation at 260 nm for 30 min giving green emission at 558 nm. Visual appearance for the emitting light varies from white, red, yellow to blue color.

Influence of alkali and alkaline earths on structural and luminescence properties of Sm3+ doped lithium fluoro phosphate glass and different (Na, Mg, K, Ca and Sr) glass ceramics

Transparent glass ceramics comprising of BiPO4 nanocrystals in bismuth phosphate glass ceramics (59.5P2O5+15Bi2O3+10BaF2+10AF+05TeO2+0.5Sm2O3 where AF= alkali and alkaline earth fluorides) doped with Sm3+ ions were synthesized by typical melt quenching route. On the basis of data obtained from differential thermal analysis (DTA), prepared samples were analyzed for their thermal stability. Further powder X-Ray diffraction (PXRD) analysis has been done for all the samples to confirm the crystalline phase of BiPO4 and short-range order i.e., isotropic. Validations of various structural units were done with the help of FTIR. Spectral intensities were obtained using Judd-Ofelt (JO) theory for various absorption bands of Sm3+ ions using least square fit method for all the studied glass and glass ceramics. Various optical parameters of Sm3+ doped lithium phosphate glass and various glass ceramics were obtained from emission and absorption spectra studied in the present work. Theses optical parameters include JO intensity parameters (Ω2, Ω4 andΩ6), radiative transition probabilites (Aed), branching ratios (β), emission cross sections (σe), absorption cross sections (∑),gain bandwidths and optical gains (σe × Δλeff and σe × τR respectively). Influence of alkali and alkaline earths metals on radiation properties of various excited levels of Sm3+ has been investigated. In relation to the other glass networks and ceramics, SrF2 glass ceramics studied in the present work exhibited productive properties and could be useful in development of optical devices for visible laser applications.

High Electronically Conductive Tungsten Phosphate Glass-Ceramics.

High electronically conductive tungsten phosphate glass-ceramics have been prepared by the controlled crystallization of binary 60WO3–40P2O5 glass in the temperature range from 700 to 935 °C and for 1 to 24 h. The substantial increase in the conductivity for four orders of magnitude is a result of the formation of electronically conductive W2O3(PO4)2 and WO3 phases. At low crystallization temperature the dominant W2O3(PO4)2 phase is created, whereas at 935 °C for 24 h the formation of semiconducting WO3 crystallites of an average size of 80 nm enhances the conductivity to the highest value of 1.64 × 10−4 (Ω cm)–1 at 30 °C. The course of the crystallization and its impact on this exceptionally high electronic transport of binary tungsten phosphate glass-ceramics has been discussed in detail. Since such highly electronically conductive WO3-based glass-ceramics have a great potential as cathode/anode materials in solid state batteries and as electrocatalysts in fuel cells, it is of interest to provide a novel insight into the improvement of their electrical properties.

Effects of Sintering Temperature Variation on Synthesis of Glass-Ceramic Phosphor Using Rice Husk Ash as Silica Source.

In this study, the authors attempted to propose the very first study on fabrication and characterization of zinc-boro-silicate (ZBS) glass-ceramics derived from the ternary zinc-boro-silicate (ZnO)0.65(B2O3)0.15(RHA)0.2 glass system through a conventional melt-quenching method by incorporating rice husk ash (RHA) as the silica (SiO2) source, followed by a sintering process. Optimization of sintering condition has densified the sintered samples while embedded beta willemite (β-Zn2SiO4) and alpha willemite (α-Zn2SiO4) were proven in X-ray diffraction (XRD) analysis. Field emission scanning electron microscopy (FESEM) has shown the distribution of willemite crystals in rhombohedral shape crystals and successfully form closely-packed grains due to intense crystallization. The photoluminescence (PL) spectra of all sintered ZBS glasses presented various emission peaks at 425, 463, 487, 531, and 643 nm corresponded to violet, blue, green, and red emission, respectively. The correlation between the densification, phase transformation, microstructure, and photoluminescence of Zn2SiO4 glass-ceramic phosphor is discussed in detail.

Preparation and luminescence properties of Dy3+ doped BaAlBO3F2 glass ceramic phosphor for solid state white LEDs

A series of BaAlBO3F2 glass ceramics (GC) phosphor with different Dy3+ concentration were prepared by melt quenching method followed by sintering process. The BaALBO3F2:xDy3+(x = 0.01,0.03,0.05,0.07,0.09 mol%) samples were characterized using X-ray diffraction (XRD), Differential Scanning Caloriemter (DSC) UV–vis diffuse reflectance spectroscopy (DRS), Transition Electron Microscope(TEM), Energy Dispersive X-ray studies (EDX), and Photoluminescence (PL).The phase formation of the prepared GC phosphor was characterized by powder X-ray diffraction (PXRD). The optimum heat treatment condition (550℃/4 h) was determined by DSC curve. The nano crystalline nature and the elemental analysis of the prepared samples were done by TEM and EDX. The absorption wavelength and the band gap value was found from the DRS spectrum. The luminescence Properties of Dy3+ in BaAlBO3F2 host were systematically studied using excitation and emission spectrum profile. Commission International de l’Eclairage (CIE) was used to study the chromatic nature of the GC phosphors. The calculated values of chromaticity coordinates were found to be located within the white light region. In addition to it, the CCT value was confirmed in the day light region. Hence the prepared materials find vast applications as white light LEDs

High-efficiency YAG:Ce3+ glass-ceramic phosphor by an organic-free screen-printing technique for high-power WLEDs

Abstract Y3Al5O12:Ce3+ glass-ceramic phosphor (YAG-GC), as a high thermal stability material, provides an efficient way to resolve the aging of phosphor-converted white light-emitting diodes in the high-power field. In the present work, transparent YAG-GCs are successfully prepared via a novel organic-free screen-printing route. The results reveal that the degradations of YAG phosphors are negligible in the as-prepared glass ceramic material. Favorable transmittance is achieved and the value is near 50%. The PL spectra intensities of YAG-GCs increase with increasing YAG doping concentration and film thickness. Superior thermal stability (87.9% of the initial value at 150 °C) and high quantum efficiency of 88.91% (decreased only 2.33% compared with the YAG raw materials) are obtained. The LE of YAG-GCs increases, while the CCT and CRI decrease with increases in film thicknesses and YAG doping concentrations. A high LE of 150.1 lm/W and an acceptable CCT of 5836 K, a CRI of 67.6 are achieved in YAG-GCs. All the results indicate that the as-prepared YAG-GCs are promising candidates in the field of high-power WLEDs.

High tantalum oxide content in Eu3+-doped phosphate glass and glass-ceramics for photonic applications

Abstract Transparent Eu3+-doped tantalum phosphate glass-ceramics containing Na2Ta8O21 nanocrystals were successfully obtained by a two-step heat treatment. Structural analyses were performed using X-ray diffraction, Transmission Electron Microscopy, Nuclear Magnetic Resonance and Raman spectroscopy. Due to the high Ta/P ratio (= 2) the glass network is built from a mixed 3D PO4–TaO6 chain in which TaO6-rich regions are inserted and responsible for crystallization of an alkali tantalum oxide phase Na2Ta8O21. Eu3+ and their optical properties was used as a sensitive probe to study it site structure in the host matrix. The radiative properties of Eu3+ emission levels were predicted using the Judd-Ofelt theory. The chemical environment and local phonon energy around the rare-earth ions have been proposed based on phonon side band associated with the 7F0 → 5D2 transition, 5D0 → 7F2/7F1 relative intensity and narrowing of the emission bands. High tantalum content precursor glass exhibits high photoluminescence quantum efficiency due to low phonon energy and high refractive index (1.9461 at 633 nm). A perovskite-like bronze crystalline structure is formed in the glass-ceramic (nucleated at 925 °C for 0.5 h and grown at 940 °C for different times) and is considered promising for nonlinear optical applications and studies.

Photo-luminescence characteristics of binary P2O5–CaO glass ceramic

ABSTRACTTo explore excellent colour display materials, the binary phosphate glass ceramics doped with R (R = Tm3+, Tb3+, Eu3+, Sm3+, and Mn2+) ions were prepared. The X-ray diffraction, transmission electron microscope, absorption, excitation, and emission spectra of the glass ceramics had been studied in detail. It was found that Ca2P2O7 and CaP2O6 had excited in the glass ceramics, which can improve the luminescent characteristics of the materials. The results show that the binary phosphate glass ceramics can display abundant colours, which is very helpful for developing the luminescent materials for colour display.

Addition of Alumina to Nanoporous Calcium Titanium Phosphate Glass-Ceramics and its Effects on Crystallization Behavior

Addition of Alumina to Nanoporous Calcium Titanium Phosphate Glass-Ceramics and its Effects on Crystallization Behavior

Transparent Yb3+ doped phosphate glass-ceramics

Yb3+ doped oxyfluorophosphate glasses with the composition (98.75) [90NaPO3-(10-x) Na2O-xNaF] - 1.25Yb2O3 (in mol%) with x = 0, 2.5, 5, 7.5 and 10 were prepared using a standard melting process. The progressive replacement of Na2O by NaF leads to an increase in the number of Q2 units at the expense of the Q1 units. This increase in the polymerization of the glass network leads to a shift of the optical band gap to lower wavelength, to a slight increase in the intensity of the emission at 1000 nm and more importantly to a change in the glass crystallization process. Indeed, both surface and bulk crystallization were observed in the glass with x = 0 while surface crystallization only occurs when NaF is added in the phosphate network. The heat treatment leads to the precipitation of at least three crystalline phases: as x increases, the NaPO3 phase grows at the expense of Na5P3O10. All glasses precipitate the Yb containing crystal, NaYbP2O7 which leads to an increase in the intensity of the emission at 1000 nm compared to the emission at 975 nm. We show for the first time to the best of our knowledge that transparent Yb3+ doped phosphate glass-ceramics can be obtained within this glass system when free of NaF.

Synthesis and characterization of iron phosphate based glass-ceramics containing sodium zirconium phosphate phase for nuclear waste immobilization

Stable sodium zirconium phosphate (NZP)-iron phosphate glass-ceramics for nuclear waste immobilization were synthesized by a melt-quenching process and the effect of B2O3 on their phases, structure and properties were investigated in detail. The results show that the NZP-iron phosphate glass-ceramics with good thermal stability and chemical durability are obtained by the melt-quenching process. It is found that B2O3 addition is the key point to achieve the glass-ceramics with NZP as crystalline phase and the reasons on the formation of NZP phase due to B2O3 addition were also analyzed and explained. The obtained conclusions indicate that the iron phosphate based glass-ceramics containing NZP phase are potential matrix for immobilizing specific nuclear waste and suggest that melt-quenching process is a possibly applicable technology to prepare certain glass-ceramics containing nuclear waste.

Crystallization behavior of Li1+xAlxGe2-x(PO4)3 glass-ceramics: Effect of composition and thermal treatment

Lithium aluminum germanium phosphate (LAGP) glass-ceramics are promising solid electrolytes for all solid-state lithium ion batteries and other electrochemical applications. LAGP glass-ceramics (Li1+xAlxGe2-x(PO4)3, x = 0.5–0.8) were synthesized using a two-step heat treatment based on characteristic temperatures from Differential scanning calorimeter (DSC) analysis. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to characterize the crystal phases and their morphologies. Our results show that high purity ion conductive phase can be obtained for the compositions with P/Ge = 2.3 and 2.4 by a two-step heat treatment, instead of the commonly adopted single step heat treatment for composition with P/Ge = 2.0. Electrochemical impedance spectroscopy (EIS) measurements show that Tg + 60%∆T (∆T = Tc-Tg) is the optimal nucleation temperature to obtain high ionic conductivity. Crystallization energies were calculated from the modified Kissinger equation based on DSC measurements and it was concluded that the crystal phase form mainly through internal nucleation. We have found in this paper that, by using a two-step heat treatment, high phase purity LAGP glass-ceramics with lower GeO2 concentration can be obtained to achieve high ionic conductivity.

Structural, elelectrical and energy storage properties of BaO–Na2O–Nb2O5–WO3–P2O5 glass–ceramics system

Ferroelectric glass-ceramics are promising composite materials with dual properties, of high dielectric permittivity and high dielectric breakdown strength. In this context, new phosphate glass-ceramics 2BaO-0.5Na2O–2.5[(1 − x)Nb2O5–xWO3]-1P2O5 (x = 0, 0.1, 0.2, 0.3 and 0.4) designated as B0, B1, B2, B3, B4 respectively, were prepared by the controlled crystallization technology and then crystallized at high temperature of 760 °C for 10 hours. Subsequently, the obtained glass-ceramics were studied by Differential Scanning Calorimetry (DSC), x-ray powder diffraction (XRD), Raman, impedance spectroscopy, and the P-E hysteresis loops. All of these techniques allowed the identification of Ba2Na4W2Nb8O30 phase with tungsten bronze structure embedded in the glassy matrix. The density of glass-ceramics was found to increase with increasing tungsten content to reach a maximum at x = 0.3 and then decreases. Dielectric and conductivity parameters were found to be governed by the presence of oxygen vacancies. Room temperature energy storage property which depends on the composition X, was performed using P-E hysteresis loops of the glass-ceramics. The optimum discharge density was obtained for B3 with an energy efficiency of 73.77%.

Ionic Conductivity of Lithium Germanium Phosphate Glass-Ceramics

In this study, the effect of induced crystallization on the electrical transport was studied in the mixed glass former glasses with the composition 40Li2O–(60 – x)P2O5–xGeO2, x = 0–25 mol %, as pot...

Tunable UV/blue luminescence in rare-earth free glass-ceramic phosphor

A novel rare-earth (RE) free feldspar glass-ceramic phosphor has been designed by a fast sintering route, following a conventional ceramic process. In this work, it is studied how subtle chemical modifications of structural elements may affect luminescence behaviour in this novel matrix. These cation additions acting as glass network former and as modifiers, 1 wt % of SiO2 and CaCO3 or Na2CO3, respectively, produce a photoluminescence enhancement up to 200%. Whereas, addition of Al2O3, a glass network former, decreases the photoluminescence emission. Raman spectroscopy evinces a correlation between photoluminescence emission and the Al,Si disorder at microscopic scale. These findings open a new challenge in order to obtain larger structural disorder to make this RE free glass-ceramic much more powerful for future optical applications, highlighting for security markers or light emitting glasses. This new phosphor might be considered as a more sustainable and low-cost alternative to RE phosphors.

Up-conversion luminescence and highly sensing characteristics of Er3+/Yb3+ co-doped borophosphate glass-ceramics

Er3+/Yb3+ co-doped phosphate glass ceramics (GC) with a cubic KAlSi2O6type structure were successfully fabricated by traditional melt-quenching technique and subsequent heat treatment. Structural characterization of the GC was achieved by X-ray powder diffractometer (XRD) combined with transmission electron microscope (TEM). The up-conversion (UC) optical properties were systemically investigated through absorption spectra, photoluminescence spectra, pump power dependent UC emission spectra, and UC decay curves. The possible energy transfer process and the transition channels were analyzed by using energy level diagram. Results show that the UC luminescence performance of the GC was enhanced compared to precursor glass (PG). Moreover, the temperature dependent UC emission spectra of the GC were measured in the temperature range of 298–798K under 980 nm laser excitation. Combined with the fluorescence intensity ratio (FIR) technique, the UC emissions of Er3+/Yb3+ co-doped GC with two thermally coupled energy levels (TCELs) of 525 nm (Er3+: 2H11∕2→4I15∕2) and 549 nm (Er3+: 4S3∕2→4I15∕2) were studied as a function of temperature in the range of 298–798K. For optimized Er3+/Yb3+ co-doped GC, the theoretical maximum value of relative sensitivity Sr−max is 1.67 % K−1 at 298 K, and absolute sensitivity Sa−max is 4.59 ×10−3 K−1 at 570 K, which indicates that the Er3+/Yb3+ co-doped phosphate GC is a very promising candidate for optical temperature sensors with higher sensitivity.

Structural analysis of Al and Si substituted lithium germanium phosphate glass-ceramics using neutron and X-ray diffraction

Li2O-Al2O3-GeO2-P2O5 (LAGP) glass ceramics (GC) has potential for use as solid state electrolyte in Li-ion rechargeable batteries with better safety and thermal stability. In this work LAGP glass-ceramics with nominal composition of Li1.5Al0.5Ge1.5P2.9Si0.1O12, have been prepared and structural studies have been carried out to understand the effect of Al3+ and Si4+substitution in place of Ge4+ and P5+. Glass was prepared using melt quenching technique and converted into glass-ceramics by controlled heat treatment. We observed that the entire glass has changed in to crystalline form. Phase formation was confirmed using XRD (X-ray diffraction) and ND (Neutron diffraction). Rietveld refinement analysis was used for structural analysis using both ND and XRD data. Analysis showed better refinement in ND and the nuclear density information of two different positions of Li+ ion (M1&M2) was revealed from Fourier maps using ND data. This helps to predict the pathway of Li diffusion in the structural units and optimize the conductivity of material. Results showed expansion of c-axis and reduction of a-axis with substitution of Al3+ in place of Ge+4. Bottleneck for Li+ ion conduction found to increase making an easier path for conduction. The study was further correlated from the recorded local structural data using X-ray photoelectron spectroscopy and Raman Spectroscopy.