Fluoride Phosphate Glasses Research Articles

Structural characterization of gallium fluoride phosphate glasses by advanced solid‐state NMR methods and correlation with photophysical properties

AbstractGallium fluoride phosphate glasses feature low refractive index, high energy radiation resistance, wide transmission range, and favorable emission characteristics of rare‐earth dopants. For the development of optimized glass compositions, a fundamental understanding of these properties in terms of glass structure is sought. We report nuclear magnetic resonance (NMR) structural studies of glasses in the system xGa(PO3)3–(40 − x)GaF3–20BaF2–20ZnF2–20SrF2 (x = 5, 10, 15, 20, and 25 mol%). 31P NMR results with 71Ga recoupling show that the network structure is dominated by P–O–Ga linkages, and no P–O–P linkages exist. 71Ga NMR results show that Ga is mainly six‐coordinated featuring a mixed fluoride/phosphate coordination. Quantitative estimates of this ligand distribution around gallium were obtained by 71Ga{31P} spin echo double resonance (REDOR) measurements. Photophysical properties suggest changes in the Eu(III) ligand distribution toward a fluoride‐dominated environment at low P/F ratio while the glass network is largely sustained by bridging oxygen atoms via P–O–Ga linkages.

Photoluminescence and X-ray induced scintillation in Gd3+-Tb3+ co-doped fluoride-phosphate glasses, and derived glass-ceramics containing NaGdF4 nanocrystals

The glass system (50NaPO3–20BaF2–10CaF2–20GdF3)-xTbCl3 with x = 0.3, 1, 3, 5, and 10 wt % was investigated. We successfully produced transparent glass ceramic (GC) scintillators with x = 1 through a melt-quenching process followed by thermal treatment. The luminescence and crystallization characteristics of these materials were thoroughly examined using various analytical methods. The nanocrystallization of Tb3+-doped Na5Gd9F32 within the doped fluoride-phosphate glasses resulted in enhanced photoluminescence (PL) and radioluminescence (RL) of the Tb3+ ions. The GC exhibited an internal PL quantum yield of 33 % and the integrated RL intensity across the UV-visible range was 36 % of that reported for the commercial BGO powder scintillator. This research showcases that Tb-doped fluoride-phosphate GCs containing nanocrystalline Na5Gd9F32 have the potential to serve as efficient scintillators while having lower melting temperature compared to traditional silicate and germanate glasses.

Extending the Palette of Luminescent Primary Thermometers: Yb3+/Pr3+ Co-Doped Fluoride Phosphate Glasses.

The unique tunable properties of glasses make them versatile materials for developing numerous state-of-the-art optical technologies. To design new optical glasses with tailored properties, an extensive understanding of the intricate correlation between their chemical composition and physical properties is mandatory. By harnessing this knowledge, the full potential of vitreous matrices can be unlocked, driving advancements in the field of optical sensors. We herein demonstrate the feasibility of using fluoride phosphate glasses co-doped with trivalent praseodymium (Pr3+) and ytterbium (Yb3+) ions for temperature sensing over a broad range of temperatures. These glasses possess high chemical and thermal stability, working as luminescent primary thermometers that rely on the thermally coupled levels of Pr3+ that eliminate the need for recurring calibration procedures. The prepared glasses exhibit a relative thermal sensitivity and uncertainty at a temperature of 1.0% K-1 and 0.5 K, respectively, making them highly competitive with the existing luminescent thermometers. Our findings highlight that Pr3+-containing materials are promising for developing cost-effective and accurate temperature probes, taking advantage of the unique versatility of these vitreous matrices to design the next generation of photonic technologies.

Impact of the O/P ratio on the optical properties and structures of fluoride–phosphate glass

AbstractCa(PO3)2–AlF3–CaF2–BaF2–BaO glasses were prepared by the melt quenching method, and the effects of the O/P ratio on the optical properties and glass structure were investigated. The bandgap energy showed no significant change at O/P = 3.0–3.4 but drastically decreased with the increase in the O/P from 3.6 to 4.0. In addition, the refractive index dispersion was analyzed based on the Lorentz model, and it was found that the decrease in the resonance frequency in the ultraviolet region with the increase in the O/P ratio resulted in an increase in the refractive index and dispersion. Analysis of the infrared absorption and Raman scattering spectra revealed that the phosphate chains were broken, and isolated Q0 units were generated with the increase in the O/P ratio from 3.6 to 4.0. Based on the structural change of the glass, the origin of the nonlinear dependence of the optical properties on the O/P ratio was discussed.

Modern magnetic resonance approaches for characterizing rare-earth containing glasses and glass ceramics

Rare-earth containing glasses are important materials with technologically relevant combinations of mechanical and optical properties. For developing their functional materials potential it is important to understand the local environment and spatial distribution of the rare-earth ions and their influence upon the structural organization of the glassy matrix. Nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) can furnish crucial information about these aspects. In this review we describe the relevant theoretical foundations with a particular focus on rare-earth containing systems. Important experimental approaches covered include dipolar NMR, paramagnetically perturbed NMR, EPR, and hyperfine interaction spectroscopies. These are illustrated in the context of various case studies, including (1) structural features of rare-earth aluminosilicate glasses, (2) spatial distribution and clustering of rare-earth dopants, (3) rare-earth ligand distributions in fluoride phosphate glasses, and structural changes along the glass-to-ceramic transformation in (4) aluminoborate and (5) oxyfluoride glasses.

BiF3 Incorporation in Na/Ba Mixed Network Modifier Fluoride–Phosphate Glasses: Structural Studies by Solid-State NMR and Raman Spectroscopies

Bismuth-containing rare-earth codoped fluoride phosphate glasses are promising materials for superbroadband near-infrared (NIR) emission with potential applications in optical amplification. To elu...

Structural study of rare earth doped fluoride phosphate glasses by solid-state nuclear magnetic resonance

A series of glasses with the compositions of 10NaF-(90-x) NaPO3-xYF3 (x = 5, 10, 15 and 20 mol%) were prepared via the conventional melt-quenching method. The structures of these glasses were characterized by multiple advanced solid-state nuclear magnetic resonance (SSNMR) techniques. Multiple phosphorus species QmnY were resolved at atomic level. Here, the value m and n denote the number of P–O–P bonds and the number of Y3+ ion bounding to phosphorus oxygen tetrahedron, respectively, which were identified by two dimensional (2D) J-resolved spectroscopy. 19F MAS spectra, 19F↔23Na and 19F↔31P rotational echo double resonance (REDOR) prove that F−ions are involved into the glass networks through Y-F•••Na and P-F•••Na linkages. The 31P {19F} J-coupling based heteronuclear multiple quantum coherence (J-HMQC) spectrum proves that F− ions selectively connect with Q1 species. F− ions show significant preference to connecting with Y3+ over P5+.

Compositional Optimization of Emission Properties for Rare-Earth Doped Fluoride Phosphate Glasses: Structural Investigations via NMR, EPR, and Optical Spectroscopies

A detailed structural investigation of two series of fluoride phosphate glasses with nominal compositions 20BaF2–20SrF2–20ZnF2–xIn(PO3)3–(40 – x)InF3 (x = 0, 5, 10, and 15) and 20BaF2–20SrF2–20ZnF2...

Spectroscopic properties of Cu2+ in alkaline earth metaphosphate, fluoride-phosphate and fluoride-phosphate-sulfate glasses

Abstract Divalent copper ions (Cu2+) are not only important colorants in consumer glasses. They can also be used as a probe for assessing the local structural arrangement within a solid host. Here, we report on the incorporation of Cu2+ into alkaline earth metaphosphate (MP), fluoride-phosphate (FP) and fluoride-phosphate-sulfate (FPS) glasses. As a d9 transition metal ion, Cu2+ exhibits a broad optical absorption band at wavelengths of 740–880 nm when incorporated into oxide glasses. The specific properties of this band are strongly affected by the local basicity of the host, which reflects in a straightforward dependence of the band position on the mean-field optical basicity in alkaline earth MP. For FP and FPS, however, distinct deviations from this simplistic correlation are found due to selective cation localization on the various oxoanions and/or halogen species. In addition, high basicity favours the formation of monovalent Cu+. Electron paramagnetic resonance indicates a transition from tetragonally distorted octahedral coordination of Cu2+ in MP to rhombohedral distortion in FP and FPS glasses.

Review on the structural analysis of fluoride-phosphate and fluoro-phosphate glasses

Fluoride phosphate/fluorophosphate (FP) glasses form an intriguing material's basis for diverse applications in optics, photonics and energy storage. The optimization of the materials' properties with regard to the application envisioned demands an understanding of the key concepts describing their local structures on different distance regimes. Because of the inevitable losses of fluoride during melting or annealing, the synthesis and elemental analytical characterization present important and critical challenges. In this contribution we summarize the current state of the literature regarding the structural characterization of these glasses. Foci are the detailed analysis of vibrational spectra with special emphasis on Raman scattering results and multinuclear solid-state NMR spectroscopy. While vibrational spectra give important information about the local environments (short range order) advanced multi-dimensional and multi-resonance methodology can extend the informational content of solid-state NMR into the sub-nanometer distance range, including second and third coordination spheres. Exemplary results will be presented for (a) aluminum fluoride based simple model systems, (b) fluoride phosphate glasses containing heavy transition metals or post-transition metal elements, and (c) rare-earth doped fluoride phosphate glasses for laser applications. The latter application field documents the utility of correlated spectroscopic studies using both methods in understanding the structural foundations of photophysical properties.

The enhancement mechanism of flowability and modulus of PET/TFP‐glass composites

Tin fluoride phosphate glass (TFP‐glass) has been found to improve the rheological properties and modulus of polar polymer, but the mechanism involved is still unrevealed. In this work, a kind of poly (ethylene terephthalate) (PET)/TFP‐glass composites with low viscosity and high modulus were prepared by melt blending. In order to explore the enhancement mechanism of flowability and modulus, we investigated the structure change of PET before and after blending, the viscosity evolution of TFP‐glass during heating and the final phase morphology of PET/TFP‐glass composites. Based on intrinsic viscosity and rheological measurements, the improvement of the flowability was attributed to the decrease of molecular weight of PET and the macromolecular plasticizer effect of TFP‐glass. Non‐isothermal crystallization behaviors of the composites indicated that the crystallization properties of PET were improved due to heterogeneous nucleation effect of the TFP‐glass and the decreased molecular weight of PET. The improved crystallization of PET as well as strong interfacial interaction between PET and TFP‐glass contribute to a significant enhancement in the modulus of composites, as compared with pure PET. POLYM. COMPOS., 40:2555–2563, 2019. © 2018 Society of Plastics Engineers

Ionic to covalent glass network transition: Effects on elastic and vibrational properties according to ultrasonic echography and Raman spectroscopy

In this study, ultrasonic echography and Raman spectroscopy were used to investigate the dependence of the elastic and vibrational properties on the composition of glass-forming pseudo-binary xSr(PO3)2-(1-x)(0.62MgF2-0.38AlF3) fluorophosphate glasses. The variation in Tg as the phosphate content increased indicated that the network in the glass structure was more interconnected. The decrease in the density with higher PO3−/F− ratios can be understood in terms of the less dense packing of the phosphate chains relative to the fluoride network and changes in the anionic volume in the glass network. The Raman spectra obtained for the fluorophosphate glasses confirmed the presence of PO4 tetrahedral species configurations with 2, 3, and 4 non-bridging oxygen atoms analogous to multicomponent mixed fluoride-phosphate glasses. A well-resolved Boson peak dominated the low-frequency Raman spectra. The transversal and longitudinal sound velocities exhibited the same composition-induced changes in the glass network as the density measurements. The variation in the bulk modulus as the PO3−/F− ratio increased indicated the transition from a strong (ionic-fluoride limit) to a less ionic (covalent-phosphate limit) structure, which was related to changes in the atomic volume. The glass network was characterized by a low cross-linking density according to the variations in Poisson's ratio. The incorporation of phosphate groups in the fluoride structure decreased the strength of the average chemical bond, as well as leading to a less interconnected network in the glass structure and reducing the strong ionic character of these fluorophosphate glasses, which was confirmed by the trend in the electronegativity difference and the attenuated propagation of the ultrasonic wave energy.

Luminescence effects in reactive powder sintered silica glasses for radiation sensing

AbstractSilica glasses doped with rare‐earth ions are potential materials for optical fiber radiation detection and dosimetry applications. High sensitivity to radiation requires fibers with large cores that can be reliably fabricated using glass made in a novel process from the reactive powder sintering of silica. The luminescence and dosimetric properties of a range of rare earth‐doped silica materials produced using this novel technique are reported here. Radioluminescence and optically stimulated luminescence (OSL) are the fundamental mechanisms enabling radiation detection in optical fibers. It was found that thermoluminescence, radioluminescence, and OSL are observed if the glass contains luminescent transitions in the detection wavelength range. Cerium‐ and thulium‐doped silica glasses were found to be promising candidates for optical fiber dosimetry. Samples showed intense luminescence signals in response to both photo‐stimulation and irradiation from alpha and beta sources. OSL results for cerium are three times larger than results for irradiated fluoride phosphate glasses previously tested for dosimetry use. Spectroscopic measurements indicate emission in the 300‐500 nm region, suitable for detection with photomultiplier tubes.

Effect of melting parameters during synthesis on the structure and properties of tin fluoride phosphate glasses

FTIR and Raman spectroscopy indicate the glass structure during synthesis of tin fluoride phosphate glass was pyrophosphate, mainly built up from Q1 end groups with a low concentration of Q2 polymeric chains. However, sub-optimal melting produced significantly higher concentrations of orthophosphate Q0 structural units. The variations in NH and P-OH vibrations in the spectra revealed that a critical time and temperature of melting were necessary for the conversion of NH4H2PO2 to produce sufficient P2O5 for glass forming. During melting, P2O5 and SnF2 form a low-temperature melt, which facilitates melting of the SnO and promotes the formation of a more stable glass structure. The fluorine breaks the POP bonds and induces depolymerisation. The density of the glass reached a maximum at 450 °C for 25 min driven by the need for conversion of NH4H2PO4 to P2O5 and miscibility of SnO in the melt. Inadequate melting times and temperatures gave low Tg values because of weak FSn and FP linkages. Glass stability improved with melting due to increased P2O5 and SnO miscibility enabling stronger SnOP linkages. The results show that melting conditions during synthesis strongly influence critical glass properties and future industrial scale-up will require an understanding of optimum processing.

Ultraviolet Upconversion Luminescence in a Highly Transparent Triply-Doped Gd3+–Tm3+–Yb3+ Fluoride–Phosphate Glasses

We report near-infrared to ultraviolet (UV) upconversion emissions in triply-doped Gd3+–Tm3+–Yb3+ fluoride–phosphate glasses. Emission at 310 nm, originated from the Gd3+:6P7/2 → 8S7/2 transition, was observed for the first time in glasses. The high-purity glasses prepared exhibit extended transparency in the UV down to 200–250 nm. The mixed fluoride–phosphate environment of the rare-earth ions was characterized by means of NMR techniques using scandium as a diamagnetic mimic for the luminescent species, for which the ligand distribution was quantified by 45Sc{31P} rotational echo double-resonance NMR. Both the intensity of the Gd3+ emission as well as those of the UV emissions at 290, 347, and 363 nm increase with increasing ratio of fluoride to phosphate ligands coordinating to the rare-earth ion.

Structure–Property Relations in Fluorophosphate Glasses: An Integrated Spectroscopic Strategy

A detailed structural investigation of a series of fluoride phosphate glasses with nominal compositions 25BaF2-25SrF2–(30–x)Al(PO3)3–xAlF3–(20–z)ScF3:zREF3 with x = 25, 20, and 15, RE = Yb and Eu, and 0 ≤ z ≤ 1.0, and of a Sc-free set of glasses with compositions w[80(Ba/Sr)F2–20AlF3]–(1–w)[80Ba(PO3)2–20Al(PO3)3] (w = 25, 50, 75), doped with 0.2 mol % Yb3+ or Eu3+, has been conducted. As indicated by Raman scattering and solid state NMR, the network structure is dominated by aluminum–oxygen-phosphorus linkages, which can be quantified by means of 27Al/31P NMR double resonance techniques. The ligand environment of the rare-earth ions is studied by (1) 45Sc NMR of the diamagnetic mimic Sc3+, (2) pulsed X-band EPR spectroscopy of Yb3+ spin probes, and (3) excitation and emission spectroscopy of Eu3+ dopants. The rare-earth ions are found in a mixed environment of fluoride and phosphate ions, which changes systematically as a function of glass composition. In the Sc-containing glasses the quantitative makeup ...

Rare-earth doped fluoride phosphate glasses: structural foundations of their luminescence properties.

We report a detailed structural investigation of a series of fluoride-phosphate glasses with different phosphate/fluoride ratios in the system xSr(PO3)2-(100 - x)[AlF3-CaF2-SrF2-MgF2] with x = 5, 10, 20, 40. Raman and multinuclear solid NMR spectroscopies confirm that the polyphosphate network structure is successively transformed to a structure dominated by Al-O-P linkages with increasing AlF3 content. Average numbers of Al-O-P linkages have been quantified by 27Al/31P NMR double-resonance techniques. The majority of the fluoride species are found in an alkaline earth metal/aluminum rich environment. The local environments for rare-earth ions have been characterized by EPR spectroscopy of Yb3+ ion spin probes and by photoluminescence experiments on Eu3+ dopant ions, including the 5D0 → 7F2 and 5D0 → 7F1 transition intensity ratio, the normalized phonon sideband intensities in the excitation spectra, and the lifetime of the 5D0 excited state. The results indicate clear correlations between these parameters as a function of composition, and confirm that even at the highest fluoride levels, there is still some residual rare-earth phosphate coordination.

Enhanced radiation dosimetry of fluoride phosphate glass optical fibres by terbium (III) doping

Fluoride phosphate (FP) glass fibres have been developed for radiation dosimetry based on the mechanism of optically stimulated luminescence (OSL). Doping with Tb3+ ions improved the materials sensitivity; for samples melted in oxidising conditions, OSL intensity was increased from 8.8 × 105 cnts/g/Gy for undoped glass to 812.3 × 105 cnts/g/Gy for Tb3+-doped glass. The radiation sensor performance of Tb3+-doped glass fibres under both beta and X-ray irradiation demonstrated the capability of the fibres for radiation dosimetry applications.

Spatially and temporally resolved temperature measurement in laser media.

A technique to measure the spatially resolved temperature distribution in a laser medium is presented. It is based on the temperature dependence of the absorption cross section close to the zero-phonon line of the active medium. Since other materials in the beam path exhibit a high (and constant) transmission at this wavelength, the method can easily be applied in realistic amplifier setups. The method was successfully tested on three different samples, which were pumped by a pulsed laser diode with up to 150 W average power: side-cooled Yb:YAG and Yb:fluoride-phosphate glass at room temperature and face-cooled Yb:CaF2 at 120 K.

Surface Analysis and Treatment of Extruded Fluoride Phosphate Glass Preforms for Optical Fiber Fabrication

Fabrication of fluoride phosphate glass optical fibers using the extrusion method for preform fabrication has been studied using the commercial Schott N‐FK51A glass. The extrusion step was found to create a surface layer of differing composition from the bulk glass material, leading to defects drawn down onto the optical fiber surface during fiber fabrication, resulting in high loss and fragile fibers. Similar phenomena have also been observed in other fluoride‐based glasses. Removal of this surface layer from preforms prior to fiber drawing was shown to improve optical fiber loss from >5 dB/m to 0.5–1.0 dB/m. The removal of this surface layer is therefore necessary to produce low‐loss fluoride phosphate optical fibers.