Precursor Glass Research Articles

Ni2+ concentration-dependent and temperature-dependent NIR photoluminescence properties in novel transparent glass-ceramics containing cubic CaTa2O6: Ni2+ nanocrystals

Novel transparent glass-ceramics (TGCs) containing cubic α-CaTa2O6: Ni2+ nanocrystals and their Ni2+ concentration-dependent and temperature-dependent spectroscopic properties were reported. They were obtained from precursor glasses (PGs) with a subsequent heat treatment, in which the PGs of 31CaO-31Ta2O5-38Al2O3-xNiO (x = 0.02–1.5 in mol%) were prepared by the aerodynamic levitation technique. A broadband near-infrared (NIR) emission with a full width at half maximum (FWHM) of ∼250 nm was observed at ∼1220 nm under excitation at 980 nm, attributing to the spin-allowed transition of 3T2g (3F) → 3A2g (3F) of Ni2+ in octahedral Ta5+ sites in α-CaTa2O6. With the increasing of NiO content, the emission intensity increases at first reaching a maximum at x = 0.3 mol%, and then declines. A red-shifting emission from 1189 to 1258 nm is observed with a broadening FWHM from 218 to 292 nm and a significantly reducing average lifetime from 594.4 to 56.0 μs. When the temperature increased from 298 to 473 K, the emission shows an apparent thermal quenching with a blue shift of 15 nm, where the intensity remained 51 % at 373 K of that at 298 K. Furthermore, it supposes that there are two types of Ni2+ active centers according to the deconvolution of the photoluminescence (PL) spectra, double-exponential fitting of the decay curves and temperature-dependent PL spectra. One shows a stronger concentration quenching, while the other exhibits a more serious thermal quenching. The possible thermal quenching mechanism was also discussed.

Tunable broadband luminescence of the novel Sn2+ doped oxyfluoride glass and glass-ceramics for W-LEDs

The demand for white-light luminescent materials for the white-light-emitting diodes (W-LEDs) field has been growing in modern life. In this work, a series of Sn2+ and Mn2+ ions co-doped highly transparent white-light emitting oxyfluoride glasses (precursor glass, PG) and Sr2LuF7 glass-ceramics (GC) were successfully prepared by the melt-quenching technique. Their luminescent and structural properties were investigated by the transmission spectra, excitation and emission spectra at different temperatures (300-500 K), luminescent decay curves, XRD, and TEM characterizations. Upon excitation with ultraviolet (UV) light, tunable broadband blue-white light emissions of Sn2+ were obtained by adjusting the concentration of Sn2+ ions. A conspicuous energy transfer process from Sn2+ to Mn2+ was observed in Sn2+/Mn2+ co-doped samples. Tunable broadband luminescence between blue-white light and orange-red light regions and nearly pink-white light emission was realized by varying Mn2+ concentration. Furthermore, compared to PG samples, the emissions were enhanced in GC samples due to the crystallization of Sr2LuF7 nanocrystals. Excellent thermal stability was also performed in these Sn2+ doped PG and GC samples with a recovering value of 96 % and 98.8 %, respectively. Simultaneously, Sn2+ doped PG and GC samples also own good optical thermal sensitivities with an SA value of 2.28 % and 2.47 % K-1, respectively. Our results indicate that these Sn2+/Mn2+ co-doped PG and GC may serve as tunable light sources under UV excitation and have prospects on the ratiometric optical thermometry fields.

Novel Tm3+/Dy3+ co-doped CaMoO4 transparent glass-ceramic phosphor for white LED applications

To develop new inorganic luminescent materials, a set of Dy3+/Tm3+ co-doped molybdate precursor glasses (PGs) were manufactured using the conventional melting method, and a novel CaMoO4 transparent fluorescent glass-ceramic (GC700-2 h) was achieved via controlled crystallization of PG at 700 ℃ for 2 h. The luminescent color of the glass phosphor was facilely modulated by varying the doping levels of Dy3+ and Tm3+. The glass phosphor with optimal doping concentration of 0.6Dy3+ and 0.6Tm3+ exhibits a color coordinate of (0.3334, 0.3107). Compared with PG, the luminous intensity and quantum yield of GC700-2 h sample is obviously increased, and GC720-2 h sample displays the color coordinate (0.3292, 0.2852), belonging to the standard white light region. Moreover, GC720-2 h sample possesses good thermal stability in fluorescence property. The white LED lamp encapsulated with GC720-2 h exhibits color temperature of 7564 K and color rendering index of 75.3. These results clearly show that the 0.6Dy3+/0.6Tm3+ co-doped glass and CaMoO4 glass-ceramic could be used as potential candidate material in the field of white light-emitting diodes.

Toughening mechanism of barium titanosilicate glass-ceramics

The fracture toughness of oxide glasses can be improved through controlled crystallization, forming glass-ceramics. However, to fully exploit their potential, an atomic-scale understanding of the toughening mechanism is needed. In this work, we investigate the structural origin of the variation in fracture toughness of barium titanosilicate glass-ceramics with varying crystallinity by combining experiments and molecular dynamics simulations. Generally, the glass-ceramics exhibit improved hardness, elastic modulus, and fracture toughness compared to the precursor glasses. The simulation results of 40BaO-20TiO2-40SiO2 glass-ceramics reveal that the differences can primarily be attributed to titanium bond switching events, namely, the change of the titanium coordination number under stress to dissipate mechanical energy. We also show that by tuning the content and aspect ratio of the formed fresnoite crystals, the fracture behavior of the glass-ceramics can be modified due to the redistribution of the stress field before fracture, which in turn controls the fracture path.

Up-conversion luminescence and energy transfer of Tm3+-Yb3+ co-doped NaLaSiO4 crystalline phase glass-ceramics

Abstract In recent years, up-conversion luminescence has attracted much attention due to its wide range of applications, and the choice of host material often determines the luminescence properties. Despite the remarkable scientific and technological development of glass-ceramics in the last decades, research on up-conversion luminescence in silicate glass-ceramics still needs to be further developed. In this research work, glass ceramics with NaLaSiO4 crystalline phase were successfully precipitated in precursor glass co-doped with Tm3+-Yb3+. The transmittance of glass-ceramics was about 73% in the visible range. Efficient up-conversion of Tm3+ with blue emission was achieved by adjusting the concentration of Yb3+ under pumping at 980 nm. The optimal concentration of Yb3+ was 0.7%, above which a concentration burst occurred. The chromaticity coordinates at the optimum luminous intensity are (0.1101, 0.1495), which are located in the blue region. The research work suggests that this glass-ceramic has potential as a blue solid-state laser.

The effect of SiO2 crystallization in enhancing the luminescence of Dy3+-Sm3+ co-doped glass ceramics for cool white light application.

The present work investigates the structural and luminescence behaviour of Dy3+-Sm3+ co-doped glass ceramics obtained through heat treatment of precursor glasses. The growth of SiO2 polycrystalline particles and evolution of these crystallites in the glass domain are witnessed via XRD and FESEM study. The presence of network vibrational bands, hydroxyl groups and the increased quantity of bridging oxygens (BOs) in glass ceramics are analysed through FTIR spectroscopy study. The absorption study (UV-Visible-NIR) showed the possible electronic transitions of Dy3+ and Sm3+ ions. The red shift in the absorption band edges and the lower bandgap values are obtained as a result of improved heat treatment in glass ceramics. Emission studies show the enhanced luminescence intensity of glass ceramics under 350 and 402 nm excitations. Decay measurement of glass ceramics showed the improved lifetimes of Dy3+ and Sm3+ ions to have appeared in microseconds (×10-6s). The colour characteristics of glass ceramics analysed using CIE colour chromaticity diagram and correlated colour temperature (CCT) values suggest the neutral to cool white light emissions. Therefore, prepared glass ceramics with SiO2 polycrystalline phase are considered to be suitable materials in cool white LEDs applications.

Amorphous-Crystalline Heterostructured Nanoporous High-Entropy Alloys for High-Efficiency pH-Universal Water Splitting.

Developing high-efficiency durable electrocatalysts in wide pH range for water splitting is significant for environmentally-friendly synthesis of renewable hydrogen energy. Herein, a facile method by dealloying designable multicomponent metallic glass precursors is reported to synthesize amorphous-crystalline heterostructured nanoporous high-entropy alloys (AC-HEAs) of CuAgAuPtPd, CuAgAuIrRu, and CuAgAuPtPdIrRu, heaped up by nanocrystalline particles with an average size of 2-3nm and the amorphous glued phase. The synthesized AC-HEA-CuAgAuPtPd owns highly catalytic performances for hydrogen evolution reaction (HER), with 9.5 and 20mV to reach 10 mA·cm-2 in 0.5m H2SO4 and 1.0m KOH, and AC-HEA-CuAgAuIrRu delivers 208 and 200mV for oxygen evolution reaction (OER). Moreover, a two-electrode electrolyzer made of the AC-HEA-CuAgAuIrRu bifunctional electrodes exhibit a low cell voltage of 1.48 and 1.49V in the acidic and alkaline conditions at 10 mA·cm-2 for overall water splitting. Combining the enhanced catalytic activities from nanoscale amorphous structure and atom-level synergistic catalyst in AC-HEAs provides an effective pathway forpH-universal electrocatalysts of water splitting.

Enhancing luminescence from visible to mid-infrared: Controllable crystallization in ZnF2-AlF3 fluoride glass-ceramics

This study presents the synthesis of innovative fluoride glass-ceramics (GCs) via a melt-quenching technique followed by heat treatment, enabling the controlled formation of ZnF2 nanocrystals within an Er3+-doped ZnF2-AlF3 fluoride glass matrix. The uniform dispersion of ZnF2 nanocrystals throughout the glass matrix was confirmed through X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. Remarkably, the crystallized glass samples retained high levels of transparency. Enhanced luminescence across visible to mid-infrared spectral regions was observed in the Er3+-doped ZnF2-AlF3 based fluoride glass-ceramics compared to their precursor glass, signaling a significant improvement. These findings underscore the potential of the developed fluoride glass-ceramics as promising materials for laser applications and mark a significant step forward in the development of fluoride crystallized fibers.

Controllable growth of Ce3+-doped fluoride nanocrystals (LaF3/KLaF4) in fluorosilicate glass

Controllable growth of nanocrystals (NCs) in optical glasses is essential to impart photonic functions for demanded applications. Here, Ce3+-doped KLaF4 and LaF3 fluoride NCs are controllably precipitated in a fluorosilicate glass via adjusting the duration and temperature of thermal treatment. The presence of phase separation in the precursor glass (PG) is derived from molecular dynamics (MD) simulations, and serves as the driving factor for the crystallization of fluoride NCs. The phase separation of PG, NCs distribution, microscopic morphology and particle size of NCs precipitated in the nano-glass composites (nano-GCs) are investigated by analytical transmission electron microscopy (TEM). Structural and spectroscopic characterizations confirm the influence of the thermal treatment on the crystalline species in the nano-GCs. The developed nano-GCs exhibit intense X-ray excited luminescence with an excellent linearity with the X-ray dosage and a good thermal stability, making them suitable for radiation detection and medical imaging applications.

Structure and optical properties of amorphous [formula omitted] thin films prepared by spin-coating using mixed n-propylamine-based solutions of [formula omitted] glass and [formula omitted] powder

Engineering new chalcogenide solids improves the desired functionality of the materials and may open the way for new applications. Here we discuss the preparation of AsxS100−x amorphous thin films modified with WS3 by the sol–gel method. We show that the formation of homogeneous, transparent, and stable n-propylamine-based solutions by mixing 0.02M AsxS100−x and 0.02M (NH4)2WS4 solutions is feasible for the As content in the chalcogenide glass precursor x ≤ 25 at.%. Above this limit, rapid and massive precipitation occurs in the solutions. We further demonstrate the preparation of amorphous thin films along the pseudo-binary AsS3- WS3 tie-line and provide information about the role of WS3 on optical properties and the structure of tungsten-based chalcogenide thin films. Due to a significant etching contrast between annealed AsS3− WS3 thin films at 70 and 240∘C, we propose tungsten-based chalcogenide thin films as a suitable platform for application in wet-lithography.

Preparation of CaO-MgO-Al2O3-SiO2 glass-ceramic with a high content of Cr2O3 using the spark plasma sintering (SPS)

2, 6, or 10 wt% of Cr2O3 was added into the CaO-MgO-Al2O3-SiO2 precursor glasses (PG), aiming to investigate the effects of high contents of Cr2O3 on the crystallization behavior and mechanical properties of glass-ceramics (GCs). The PGs were milled into powder and then sintered by spark plasma sintering (SPS) technology at 750∼850 °C under the pressure of 10 MPa. It was found that Cr2O3 induced the precipitation of spinel nuclei in the PGs, which served as the heterogeneous nucleation sites for the augite crystals. Augite and spinel were the main phases of the GCs, and the crystallinity increased by increasing the Cr2O3 addition amount and sintering temperature. The GC prepared at 850 °C with 6 wt% Cr2O3 addition showed excellent bending strength, with Vickers hardness, and fracture toughness of 214 MPa, 8.2 GPa, and 1.3 MPa·m1/2, respectively.

Transparent Glass Composite Scintillator with High Crystallinity for Efficient Thermal Neutron Detection

AbstractThe sensitive and rapid detection of thermal neutrons holds significant importance in various fields such as energy utilization, medical treatment, and national defense. However, the available thermal neutron scintillator is difficult to reach this target, mainly limited by the optical and scintillating performance. Herein, the in situ crystallization strategy of glass to construct scintillation glass composites for efficient thermal neutron detection is proposed. The congruent crystallization of the hybridized alkali earth silicate glass system may not only achieve high crystallinity, but also will keep the refractive indexing matching between the precipitated crystal and precursor glass phases. The prepared glass composites feature high luminescence efficiency, optical transmission and excellent neutron response properties. These factors collectively contribute to the robust neutron scintillation performance with a light output of ≈36 000 photons/neutron, which represents the highest value among glass‐based scintillators. Moreover, the composite configuration brings about the additional function of thermal neutron and γ‐ray discrimination. By using this composite scintillator, the neutron detector is constructed and demonstrates its application for detecting thermal neutron and distinguishing it from γ‐ray in an online way. The studies prove that glass composites with high crystallinity are expected to be promising candidates for a new generation of multifunctional neutron detectors.

High color‐purity broad orange‐red emission of Mn2+‐doped transparent phosphate glass–ceramics embedded NaYP2O7 crystals

AbstractIn this work, novel Mn2+‐doped transparent NaYP2O7 glass–ceramics were prepared through melt‐quenching and subsequent thermal treatment. The surface crystallization method was confirmed based on the differential scanning calorimeter, X‐ray diffraction, and scanning electron microscope characterization. As the increase and prolong of the heat‐treatment temperature and time, the crystallinity of the NaYP2O7 glass–ceramics increases, while the transmittance gradually decreases. The optimal heat‐treatment regime is identified to be crystallized over 4 h at 580°C based on the crystallinity and transmittance. Under the excitation of 408 nm, both the Mn2+‐doped precursor glass and glass–ceramic crystallized at 580°C for 4 h generate a broad emission at 620 nm (4T2(g)→6A1(s)) with a full width at half‐maximum (FWHM) of ∼107 nm. The glass–ceramics exhibit higher emission intensity and longer decay lifetime than that of precursor glass with the aid of the low phonon energy NaYP2O7 crystals. The Mn2+‐doped glass–ceramic exhibits stable orange‐red luminescence with the chromaticity coordinates of (0.568, 0.428), low correlation color temperature of 1 800 K, high color purity of 98.88%, and low thermal quenching (70% at 373 K of the initial intensity at 298 K). The above results indicate that Mn2+‐doped transparent NaYP2O7 glass–ceramics have promising potential for orange‐red color display devices.

Dy3+‐ and/or Sm3+‐doped glass–ceramics containing NaGd(MoO4)2 crystalline phase for warm white light applications

AbstractThe transparent glass–ceramics with Dy3+ and/or Sm3+ doping, which include the NaGd(MoO4)2 single‐crystal phase, were synthesized using the melt‐quenching method followed by heat treatment in the SiO2–B2O3–Na2O–ZnO–MoO3–Gd2O3 system. The formation and fluorescent properties of Dy3+ single‐doped precursor glasses were thoroughly examined, and the optimal doping amount of Dy2O3 was determined to be 0.3 mol% by fluorescence spectroscopy. The ideal heat treatment procedure for glass–ceramics containing Dy3+ and Sm3+ was determined to be crystallized at a temperature of 650°C for a duration of 7 h. After undergoing heat treatment, the luminescence performance of glass–ceramic is significantly boosted, exhibiting an improvement that is roughly twice as substantial when compared to the precursor glass. Extensive research has been conducted to thoroughly examine the fluorescence capabilities of glass–ceramics doped with both Dy3+ and Sm3+, and the intricate mechanism of energy transfer has been extensively explored. The transparent glass–ceramics doped with Dy3+ and Sm3+ and containing NaGd(MoO4)2 crystal phase can produce tunable luminescence from yellow to orange with a high color purity and a low correlated color temperature, which indicates that they have the potential to be applied to warm white light scenes such as household lighting under ultraviolet excitation.

Diversely phased glass-ceramics in Bi2O3–SiO2 system for heterostructure formation: A demonstration via visible-light-sensitive photocatalytic reaction

Structural ordering in the glass phase during heating processes (i.e., crystallization) creates aggregate textures with diverse phases in ceramic materials. In this study, we focused on a glass-ceramic technique as a new approach for the formation of heterostructures enabling electronic interactions between different crystallized phases. In this study, we fabricated diversely phased glass-ceramics (DPGCs) from a binary Bi2O3–SiO2 glass precursor and investigated the visible-light-responsible photocatalytic reaction. We found the co-precipitation of metastable Bi2SiO5 and δ-Bi2O3 phases in the heat-treated precursor, and the resulting DPGCs were confirmed to show remarkable photocatalytic activity under visible light irradiation, ascribed to the heterojunction between the Bi2SiO5 and δ-Bi2O3 phases. This study not only demonstrates the heterostructure using DPGCs but also has practical significance in contributing to the mass production of visible-light-responsive photocatalysts using simple heat treatment.

Highly efficient luminescent solar concentrators based on selective laser-induced crystallization in CsPbBrxCl3−x (x = 0–3) doped glass

The optical conversion layer with CsPbBrxCl3 − x (x = 0 − 3) NCs linear array was prepared in the precursor glass by femtosecond laser direct writing.

Structure, spectroscopic properties and optical temperature sensing behavior of glass-ceramics containing polymorphic CaTa2O6: Er3+/Yb3+ nanocrystals

Novel glass-ceramics (GCs) containing polymorphic CaTa2O6: Er3+/Yb3+ nanocrystals are prepared by aerodynamic levitation method following with a heat-treatment of the precursor glasses (PG). Phase transition from cubic to orthorhombic crystal...

Infrared transparent CaO–Ta2O5–Al2O3 glass-ceramics with high microhardness: Crystallization behavior and microstructure development

Infrared (IR) transparent materials with longer optical window and higher mechanical properties are highly demanded in optical communication, IR imaging, sensing and laser optics. Although transparent ceramics have higher mechanical strength, their production is still difficult using conventional sintering techniques. Herein, new IR transparent CaO–Ta2O5–Al2O3 glass-ceramics (TGCs) containing cubic ɑ-CaTa2O6 nanocrystals are reported. They exhibit a broadband transmitting window (0.5–5.5 μm) with high IR transmittance (∼80 %) and high refractive indices (nd = 1.96, n1530 = 1.93). The effects of heat treatment holding time on the structure and properties of TGCs are investigated. A slightly increased proportion of crystalline phase is determined by Rietveld refinement. 27Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy reveals that partial Al[4] and almost all Al[5] in the precursor glass are converted to Al[6] in the residual glass after crystallization. CaTa2O6 nanocrystals with amorphous shells are present within the nanodroplet domains, and a significant Ta enrichment is clearly observed. A confined crystallization process is proposed to understand the heat treatment time dependent structural characteristics and mechanical properties of the obtained TGCs. Vickers hardness (HV) of 12.01 GPa and Young's modulus (E) of 248.8 GPa are achieved in TGCs, making them promising candidates as high-performance IR materials for optical applications.

Effect of thermal poling in sodium tantalum phosphate glass-ceramics

Eu3+-doped sodium tantalum phosphate glass-ceramics containing bronze -like perovskite crystalline phase Na2Ta8O21 were obtained with different crystalline states (degree of crystallinity and average crystallite size) by a suitable control of the heat-treatment time and temperature of the precursor glass. Luminescence properties of Eu3+ in these materials are in agreement with a progressive insertion of the rare earth ions in the sodium tantalate Na2Ta8O21 phase, as probed by a clear decrease of the intensity ratio between transitions [5D0 →] 7F2/7F1 and narrowing of characteristic emission bands. Thermal poling insights were performed on these glassy and glass-ceramic materials and the experimental conditions had to be carefully optimized in the glass-ceramics to avoid electrical sparks and sample break associated with dielectric breakdown of the samples. Suitable and stable thermal poling treatments could be performed at 250 °C and 900 V under N2 atmosphere on both glass and glass-ceramics. These first insights pointed out a lower migration kinetic of sodium ions when compared to the precursor glass as well as a lower content of depleted ions, since part of sodium is supposed to be “frozen” inside the crystalline phase in glass-ceramics. Despite these lower kinetic poling conditions, a poled sodium depleted layer whose thickness depends on the poling time was successfully formed at the anode side. Reflectance infrared spectroscopy was also used to investigate the structural changes in the poled layer. These IR data pointed out that structural changes induced by thermal poling are mainly promoted in the phosphate network rather than tantalate units in both glass and glass-ceramics in agreement with a selective sodium migration from the remaining glassy phase. Macroscopic induced SHG measured by the Maker fringes technique is also consistent with the EFISH model and quantitative simulations of these data allowed to estimate second order nonlinear optical susceptibilities χ(2) ten to twenty times lower in the glass-ceramics than in the precursor glass. Such electric behavior is discussed in terms of dielectric properties of heterogeneous materials and interfacial polarization mechanisms between crystallites and glassy phase.

Judd-Ofelt analysis and NIR spectroscopy properties of Nd3+-doped Na2O/NaF-Al2O3-Y2O3-P2O5 glass and transparent glass-ceramics containing NaYP2O7 crystals

In the present work, the Nd3+-doped Na2O/NaF-Al2O3-Y2O3-P2O5 glass and transparent glass-ceramics were fabricated by conventional melting-quenching and subsequent heat treatment. The glass structure was studied by XRD, DSC, and FTIR spectrum, the fluorophosphate glass exhibits a more compact cross-link network. The UV–Vis–NIR absorption spectra, Judd-Ofelt theory, and photoluminescence spectra were used to explore the absorption and NIR spectroscopic features of the Nd3+-doped phosphate and fluorophosphate glasses. Under the excitation of 582 nm, the intense NIR emission in the Nd3+-doped glasses originating from the internal transition 4F3/2 → 4IJ/2 (J = 13, 11 and 9) was observed, and the transition 4F3/2 → 4I11/2 (1053 nm) is the most dominate. The transparent glass-ceramics (GC) was fabricated via heat treating on the precursor glass (PG) at Tg+100 °C, and the precipitation of NaYP2O7 crystals in GC was confirmed by XRD and SEM. With the benefit of the existence of the NaYP2O7 crystals, the Nd3+-doped GC exhibits higher NIR emission intensity, higher quantum efficiency (72.85% and 84.11%), larger σ(λp) values of 4.24×10-20 cm2 and 4.86×10-20 cm2, larger σ × Δλeff values of 10.22×10-26 cm3 and 11.67×10-26 cm3 than that of PG. These results indicate that the Nd3+-doped phosphate and fluorophosphate glasses and glass-ceramics may be used as a gain medium for 1053 nm laser emission.