Metaphosphate Glasses Research Articles

Engineering the meta-phosphate BaO–Al2O3–P2O5 glass network for high average power (HAP) laser applications: Systematic composition modifications and SiO2 integration

The metaphosphate glasses are the preferred gain media for high-power solid-state laser applications. In the context of solid-state glass lasers, the main challenge to attain high average power (HAP) is to govern excessive thermal loading during operation. This work focuses on addressing thermal loading issues through improving thermal and mechanical properties of the meta-phosphate BaO–Al2O3–P2O5 laser glass system by engineering its molecular structure through systematic composition modifications with SiO2 incorporation. FTIR, Raman and 27Al MAS-NMR spectroscopy indicate stronger P–O–P bridges with decreasing glass basicity and increasing [AlO4] formations beyond 12.5 mol% Al2O3. The O/P ratio increases from 3.05 to 3.43 with up to 20 mol% SiO2 in Series-A and from 3.13 to 3.49 with up to 15 mol% SiO2 in Series-B, altering the Al coordination number from 6 to 4 to maintain the glass network charge balance. Increased [AlO4] formation raises Young's modulus from 61 GPa to 73 GPa and decreases Poisson's ratio from 0.30 to 0.24. These changes enhance fracture toughness and reduce CTE. Further, SiO2 inclusion enhances thermal conductivity by increasing glass network compactness and rigidity. These modifications highlight the improved thermo-mechanical properties of the SiO2-modified Series-B glasses. Yb3+ emission cross-section rises from 0.495 × 10−20 cm2 in ABSP-A1 glass to 0.502 × 10−20 cm2 in ABSP-B1 with increased [AlO4] formation. More AlPO4-like units in ABSP-B1 increase average glass phonon energy, reducing Yb3+ fluorescence lifetime from 1062 μs to 945 μs, whereas SiO2 addition boosts Yb3+ fluorescence lifetime again. Lower OH− content further extends Yb3+ fluorescence lifetime in Series-B glasses with higher SiO2 content. This study underscores the intricate relationship between glass molecular structure and thermal, mechanical, and spectroscopic properties, advancing high-power silico-phosphate laser glass development.

Charge transport mechanism and mechanical properties of rubidium cerium metaphosphate glasses

Cerium-doped glasses usually contain a mixture of Ce3+ and Ce4+ species, with the trivalent state being dominant. Quantitative determination of the redox ratio is complicated by the narrow energy gap between both states, leading to spectral overlap in optical absorption studies, and strong beam sensitivity in other techniques. However, it also indicates a way to induce electric conduction through electron hopping, with the additional benefit of visual transparency. Here, cerium phosphate glasses are reported in which the local optical basicity is varied through substitution of cerium by highly polarizable rubidium ions. This is done in order to control the Ce3+/ Ce4+ ratio. Electrical impedance spectroscopy is considered as an alternative means to assess the redox ratio by exploring the extent of polaron conduction. Complementary Raman and 31P MAS NMR spectroscopic studies provide structural insight on the process of mixed electronic and ionic charge transport. Meanwhile, a monotonic decrease in the elastic modulus and an abnormal change in Poisson's ratio when varying the composition corroborate structural interpretations.

Atomistic origins of deformation-induced structural anisotropy in metaphosphate glasses and its influence on mechanical properties

Glasses are generally isotropic. However, structural anisotropy can be induced through processing. Here, molecular dynamics simulations were used to study the deformation behavior of metaphosphate glasses and the atomistic origins of the deformation-induced structural anisotropy. The anisotropy observed in the metaphosphate glasses originates from a preferred orientation of the tetrahedral units at both short- and medium-range, depending on the loading mode. The mechanical behavior of the glasses showed that the Young’s modulus of the anisotropic glasses is lower than that of pristine glasses. Pre-deformed glass shows a clear directional dependence with respect to the axis of the pre-deformation. In general, the Young’s moduli of the pre-deformed glasses are lower than those of pristine glasses. These findings provide insights into the origin of deformation-induced anisotropy in metaphosphate glasses and its influence on their mechanical properties, thus providing important insight for the rational design of oxide glasses with tailored material properties.

Structural, mechanical and electrical characteristics as well radiation attenuation capacities of barium lithium meta-phosphate glasses

Structural, mechanical and electrical characteristics as well radiation attenuation capacities of barium lithium meta-phosphate glasses

Influence of barium substitution on the physical, thermal, optical and luminescence properties of Sm3+-doped metaphosphate glasses for reddish orange light applications.

Our present study focuses on examining the thermal, structural and luminescent characteristics of sodium barium metaphosphate glasses doped with Sm3+. Glass samples with molar compositions (100 - y)[(50P2O5)-(50-xNa2O)-(xBaO)]-ySm2O3, where x = 20, 25, 30, 35, 40 and y = 0.3 and 1% were first synthesized by conventional melt quenching and later dehydroxylated under a constant N2 flow to ensure final glasses with a very high degree of chemical and optical homogeneity and free of water. Upon the addition of BaO and Sm2O3, refractive index, molar mass, density, glass transition temperature and dilatometric softening temperature exhibited an increase, whereas the coefficient of thermal expansion showed a decrease. The FTIR spectra analysis reveals a network depolymerization that intensifies with rising BaO concentration, ultimately transitioning from a modifier oxide to a glass-forming element, at higher BaO concentrations. All doped samples exhibited prominent absorption bands in the visible (VIS) and near-infrared (NIR) regions, as revealed by the optical absorption spectra. The Na2O modifier demonstrated greater influence on Sm3+ emission compared to BaO, a phenomenon that can explained by the moderation of the local ligand field strength resulting from this substitution. With an increase in Sm2O3 concentration from 0.3 to 1 mol%, the experimental lifetimes of the 4G5/2 level decrease, primarily attributed to the presence of energy transfer mechanisms. A discussion of Judd-Ofelt parameter analysis and glass radiation properties will be presented.

Effects of ionic cross-linking on the non-exponentiality of the [formula omitted]-relaxation in metaphosphate glass melts as measured by dynamic light scattering

Photon correlation spectroscopy was conducted on a series of metaphosphate glass melts to measure the liquid's dynamic structure factor near the glass transition and thereby characterize the degree of non-exponentiality in its time decay. Each metaphosphate consists of polymeric chains of [PO4]−1 monomers interspersed by a variety of modifying cations (Ag+, Ba2, Ca2+, Sr2+) which can potentially form inter-chain crosslinks via ionic bonding. Our results show that the non-exponentiality of the α-relaxation decreases monotonically with increasing field strength of the cation-oxygen bond.

Magnesium-copper metaphosphate glasses – A more detailed chemical view

In order to study the binding possibilities of Mg(II) and Cu(II) and their influence on the chemical composition and properties of xCuO-(50-x)MgO-50P2O5 metaphosphate glasses, these glasses were prepared on the entire composition line. Based on the results of X-ray fluorescence, Raman spectroscopy, electron paramagnetic resonance and 31P MAS NMR, a real chemical composition, i.e. a chemical model, was proposed. The proposed chemical model was verified using the results of various experimental methods characterizing the properties of both the volume and the surface of the glasses, e.g. dilatometry, DSC, Raman spectroscopy and tenziometry. The assumption of the influence of the shielding of the charge of the copper core by its d9 valence electrons was also verified. The experimental results obtained by all the techniques used are discussed in detail.

Energy transfer mechanisms and non-radiative losses in Nd3+ doped phosphate laser glass: Dopant concentration effect study

The aim of the present work is to show a simple quantitative theoretical study on the relaxation mechanisms of the 4F3/2 levels of the Nd3+ ions in the widely used meta-phosphate laser glass system (P2O5–Al2O3–BaO–K2O) for the studied concentration range of the Nd3+ ions from 0.10 × 1020 to 8.15 × 1020 ions/cm3. Auzel's diffusion-limited model for energy transfer has been adopted in the present study for estimating zero concentration level lifetime, τ0 of 4F3/2 levels in the Nd3+ ions present in the studied glass matrix. Primarily, the relaxation mechanisms are dominated by radiative decay (krad) and energy transfer to hydroxyl groups (kOH) present in the glass network structure up to the dopant, Nd3+ concentration 0.78 × 1020 ions/cm3. Later on, with increasing dopant ion concentration, fluorescence from trivalent Nd3+ ions is unfortunately quenched by the interaction between Nd3+ ions, also known as concentration quenching. The concentration quenching of the fluorescence lifetime has been analysed using proposed Inokuti-Hirayama (I–H), Yokota-Tanimoto (Y-T) and Brushtein (B) models and found to be migration-assisted cross-relaxation mechanisms at or beyond 1.47 × 1020 ions/cm3 dopant concentration. The diffusion coefficient, D derived from the Y-T model and the energy migration rate, Wm attained from the B model has demonstrated diffusion-based energy migration initially at about >1.47 × 1020 ions/cm3 Nd3+ concentration and after that, it has switched to a hopping mechanism with further increasing ion concentration, >2.97 × 1020 ions/cm3. Critical quenching concentration, Q and critical radius, R0 for the studied glass composition have also been determined and correlated to the experimental results. No evidence for ion clustering has been found within the studied dopant ion concentration range (0.10 × 1020 - 8.15 × 1020) ions/cm3 with respect to the estimated R0. Finally, the contribution of the individual relaxation process to the experimentally recorded emission spectra and measured lifetime, τexp has been investigated in order to identify the most suitable Nd3+ ion concentration for developing large-aperture high-energy/high-peak-power lasers and optical amplifiers. Therefore, the present work is expected to be significant in aiding to formulate an effective glass composition for construction of compact high-power lasers and optical amplifiers.

Spectroscopic properties of Er3+-doped barium phosphate glasses for optical gain media

Barium metaphosphate glasses (PBaLa) doped with erbium (Er3+) ions have been prepared by melt quenching method and studied their optical, structural characteristics by using FT-IR, absorption, radiative de-excitation spectra, decay curves and up-conversion measurements. Judd-Ofelt (Ωλ, λ = 2,4 and 6) parameters have been determined using the absorption transitions of the Er3+(1.0 mol %)-doped glasses which are in turn taken to predict the radiative characteristics that include branching ratio (βR), radiative emission probability (AR) and lifetime (τR) of some important fluorescent levels of Er3+:glasses. Visible emission spectra measured under 378 nm excitation reveals three emission transitions at 663 (4F9/2 → 4I15/2), 547 (4S3/2→ 4I15/2) and 524 nm (2H11/2 → 4I15/2) corresponding to Er3+ ions. Among these, the green emission at 547 nm is relatively intense. Near-Infrared emissions were measured by exciting at 980 nm which exhibits broad emission at 4I13/2→ 4I15/2 (1.53 µm). The stimulated emission cross-section (σemi), FWHM and gain bandwidth (σemi× FWHM) were predicted to be 13.58 × 10-21 cm−2, 59 nm and 801.2 cm3, respectively, for PBaLaEr1.0 glass. The lifetime of 4I13/2 level has been shortened from 2.53 to 0.8 ms with an increase in Er3+ ions concentration from 0.1 to 2 mol %. NIR to visible up-conversion has also been measured for various concentrations of Er3+-doped PBaLaEr glasses with 980 nm excitation. These findings indicate that the Er3+-doped PBaLaEr glasses can be considered for waveguide laser and optical amplifier applications at 1.53 µm.

New Mg/Sr phosphate bioresorbable glass system with enhanced sintering properties

Phosphate glasses are ideal candidates to substitute traditional silicate bioactive glasses as they can exhibit controlled ion release. Furthermore, phosphate glasses possess congruent dissolution and also resistance to crystallization, two properties that are favorable for the processing of 3D porous scaffolds. However, most of the phosphate glasses also exhibit a fast dissolution rate, which is inappropriate for bone tissue regeneration. In this context, a new bioresorbable phosphate glass within the 45P2O5- 2.5B2O3- 2.5SiO2- 10Na2O- 20CaO- (20-x) SrO- (x)MgO (in %mol) composition was developed. Magnesium is substituted for strontium in order to promote bone formation but in the present study, its role is mainly to favor sintering at lower temperatures without crystallization. The in vitro dissolution in simulated body fluid was assessed for glass particles <38 μm (pH, ICP, SEM-EDS). All glasses were found bioresorbable, rather than bioactive. The newly developed phosphate glasses containing Sr and Mg were found to have a slower dissolution rate when compared to traditional metaphosphate glasses while maintaining their congruent dissolution and hot forming ability. All glasses were 3D printed into scaffolds with controlled pore size and without apparent crystallization. The substitution of SrO for MgO was shown to be highly effective in enhancing the sintering ability of the material by enabling sintering at lower temperatures while avoiding the risk of crystallization leading to the processing of scaffolds with mechanical properties, in compression, above that of the cancellous bone.

Elasto-mechanical and gamma radiation/neutron shielding effectiveness behavior of sodium metaphosphate glasses under different oxidization conditions: Effects of zircon ions

This repot aims to probe the physical, mechanical and radiation-protecting properties of a series of glasses with a chemical composition of yZrO2+(24.5-y)CaO+24.5Na2O+ 6P2O5+45B2O3 (0.5<y<5.0 mol%). The mechano-shielding characteristics of the glasses are discussed in terms of the molar ratio [ZrO2]/[CaO]. Glasses elastic-moduli are calculated utilizing the Makishima-Mackenzie model, along with Poisson's ratio (PR). The mass-attenuation-coefficient (MAC) of these samples is numerically evaluated in the energy range 0.015<E<15 MeV using the Phy-X/PSD online code. The computed MAC is used to derive significant radiation protection factors such as the linear attenuation coefficient (LAC), half-layer value (HVL), effective (Zeff)- and equivalent (Zeq) atomic number. The G-P fit method is employed to determine the exposure (EBF) and energy absorption (EABF) buildup factors for the glass set. Additionally, an assessment of the fast neutron removal cross-sections (ΣR) of the glasses is conducted. The study determined that the glass composition containing 5ZrO2–19.5CaO–24.5Na2O–6P2O5–45B2O3 (in mol%) demonstrated the most favorable properties for radiation protection implementations compared to the other glasses. Therefore, it can be inferred that the examined glasses demonstrate significant promise for protecting against radiation in both indoor and outdoor settings.

Post-glass melting synthesis and photochromic properties of composite AgCl-AgPO3 glasses

We herein present a simple, fast, low-temperature, post-glass melting fabrication protocol in which a photochromic silver cation based modified zone is incorporated within silver metaphosphate glass (AgPO3). The selection of AgPO3 glass is mainly based on its relative “soft” nature (Tg = 192 °C) that enables the integration of silver cations from the surface deposited AgCl layer, while being transparent in most of the visible range, and therefore suitable for smart photochromic window applications. The suggested synthesis procedure permits the controlled formation of a silver cation modified layer within the host glass matrix, while the characteristics of the layer itself can be adjusted correspondingly. Our findings reveal a direct relationship between the developed composite AgCl–AgPO3 glass photochromic response and the morphological features of the integrated layer, i.e., thickness and position. More importantly, the photochromic response time with various UV irradiation doses is also studied, where remarkable response times of several seconds are obtained. Processes and efforts to further enhance the photochromic performance by utilizing the presence of silver nanoparticles within the glass matrix are also presented and discussed.

Thermoluminescence properties of Er-doped borophosphate glass for beta radiation

The thermoluminescence (TL) dosimetric properties of metaphosphate glass system were investigated. The glass system of (Er2O3)1-(SrO)24-(B2O3)25-(P2O5)50 was prepared using a melt quenching technique. The glass system was characterized using different techniques. The internal structure of the system was probed with XRD and FTIR technique was used to identify the types of bonds between the involved atoms. The analysis of TL glow curve was studied by different methods and was found to be composed of six trap peaks at energies 0.817, 0.846, 0.958, 1.190, 1.248, and 1.347 eV. The TL dose–response signal was found to be linear in the range of 0.22–55 Gy. The activation energies were determined by three methods: glow curve deconvolution (CGCD), Tmax-Tstop method and Peak shape (PS) methods. The results of the three methods exhibited a good agreement with each other. Highlights The thermoluminescence properties of metaphosphate glass were investigated. The glass samples were irradiated to different doses of beta particles. The deconvolution indicated the presence of six overlapping glow peaks. The activation energies were determined by three methods and the results of all the methods exhibited a good agreement.

Resolving the mixed-alkali effect on the viscoelastic behavior of supercooled liquids

Relaxation processes in mixed-alkali metaphosphate glasses and supercooled liquids are studied using a combination of calorimetric, electrical impedance spectroscopic and rheological measurements to investigate the atomistic nature of the mixed-alkali effect (MAE) on the glass transition temperature Tg and viscous flow. While Tg and fragility index of single-alkali liquids are controlled by the segmental motion of phosphate chains, the mixed-alkali liquids exhibit the presence of a second relaxation process, which is slower than chain motion and is characterized by a lower activation energy. This process is assigned to the scission and renewal of P-O bonds that relieve the accumulated stress in the network resulting from its matrix-mediated coupling with pairwise hopping of dissimilar alkalis. The viscous flow and glass transition in mixed-alkali phosphate liquids appear to be controlled by this P-O bond scission-renewal process, which is shown to be consistent with a lowering of their fragility index and a concomitant decrease in the stretching exponent of structural relaxation, compared to their single-alkali counterparts.

Laser-Induced Erasable and Re-Writable Waveguides within Silver Phosphate Glasses.

Femtosecond direct laser writing is a well-established and robust technique for the fabrication of photonic structures. Herein, we report on the fabrication of buried waveguides in AgPO3 silver metaphosphate glasses, as well as, on the erase and re-writing of those structures, by means of a single femtosecond laser source. Based on the fabrication procedure, the developed waveguides can be erased and readily re-inscribed upon further femtosecond irradiation under controlled conditions. Namely, for the initial waveguide writing the employed laser irradiation power was 2 J/cm2 with a scanning speed of 5 mm/s and a repetition rate of 200 kHz. Upon enhancing the power to 16 J/cm2 while keeping constant the scanning speed and reducing the repetition rate to 25 kHz, the so formed patterns were readily erased. Then, upon using a laser power of 2 J/cm2 with a scanning speed of 1 mm/s and a repetition rate of 200 kHz the waveguide patterns were re-written inside the glass. Scanning electron microscopy (SEM) images at the cross-section of the processed glasses, combined with spatial Raman analysis revealed that the developed write/erase/re-write cycle, does not cause any structural modification to the phosphate network, rendering the fabrication process feasible for reversible optoelectronic applications. Namely, it is proposed that this non-ablative phenomenon lies on the local relaxation of the glass network caused by the heat deposited upon pulsed laser irradiation. The resulted waveguide patterns Our findings pave the way towards new photonic applications involving infinite cycles of write/erase/re-write processes without the need of intermediate steps of typical thermal annealing treatments.

Probing the effect of a glass network on the synthesis and luminescence properties of composite perovskite glasses [Invited

All-inorganic cesium lead bromide perovskite nanocrystals (PNCs) are highly promising candidates for various optoelectronic and photonic devices. However, poor stability upon exposure to moisture and lead toxicity issues significantly limit their applications. A modern and promising strategy on resolving these issues is the encapsulation of highly luminescent (PNCs) within transparent inorganic oxide glasses. While the encapsulation procedure effect on the development and properties of the so-formed PV-Glasses has been explored in detail, there is lack of understanding the influence of the selected glass composition and network type on the outcome of the synthesis. Herein we report on the synthesis and photoluminescence properties of composite perovskite-glasses upon growing all-inorganic lead halide perovskites within three different types of inorganic oxide glasses. When a silver metaphosphate glass matrix is used it is revealed that the low glass transition temperature of the phosphate glass limits significantly the temperature range of the required post-melting annealing treatment, while the lead salt precursors react with the phosphate entities of the network destroying the stoichiometry of the PNCs. As a result the formation of PNCs is hindered. As a consequence, a double network former borophosphate glass was employed as a suitable host. While annealing treatments at higher temperature were facilitated in this case, it is found that the high silver content becomes an obstacle for the perovskite formation. In view of these findings, cesium lead bromide (CsPbBr3) and cesium lead iodide (CsPbI3) composite perovskite borate glasses were synthesized and found to be suitable hosts. Indeed, such composite glasses exhibit interesting photoluminescence properties that are compared with those of PNCs outside the glass matrix.

Effect of the manganese-cobalt substitution on the micro-hardness and thermal properties of zinc phosphate glasses

Metaphosphate glasses belonging to the 10ZnO-(40-x)CoO-xMnO2-50P2O5 system, with 0 ≤ x ≤ 40 mol%, have been synthesized by the melt-quenching technique. The obtained glasses are colored. Some physical parameters such as density, molar volume, and packing oxygen density are determined. It is observed that all these parameters are composition-dependent. The density and molar volume decrease and increase as MnO2 content increases, respectively. Thermal properties were studied with a differential thermal analysis. The glass transition temperature (Tg), crystallization temperature (Tc), and the thermal stability (ΔT) of each glass are evaluated. It is found that glass transition temperature (Tg) and the ionocovalent crosslink density (ICd) decrease with increasing the Mn/Co ratio. It is worth noting that the highest value the thermal stability (ΔT = 192 °C) is obtained for the glass containing high-MnO2 content (x = 30 mol %). The effect of MnO2 on the rigidity of the glasses is also studied by the determination of the micro-hardness (Hv) values. It is observed that this parameter increases with increasing of MnO2 content. This trend is explained according to the bond strength.

Insight into the structure of magnesium and sodium mixed phosphate glasses: A molecular dynamics study

Three phosphate glasses from the series (50-x/2)Na2O–xMgO–(50-x/2)P2O5 (x = 20, 30 and 40) were studied using classical molecular dynamics simulation. In addition, the metaphosphate compositions of 50MgO-50P2O5 and 50Na2O-50P2O5 were also modelled. The model results showed good agreement with the experimental results considering reported experimental uncertainties. Both Na and Mg act as network modifiers. The magnesium metaphosphate glass model showed that the local environments of the magnesium consist of distorted structures with mean coordination number of 4.4, while the Na-O mean coordination number is found to be 5 in sodium metaphosphate composition. For sodium magnesium phosphate glasses, the models show that Mg-O coordination number has no change over the range of the target compositions with an average of NMgO =4.4 and the mean distance at 1.99 Å. There is also no noticeable change in Na-O coordination number ∼5 and the Na-O distance is found at 2.41 Å in sodium magnesium phosphate glasses. The depolymerization of the phosphate glass network is observed upon the addition of MgO. The relative amounts of bridging Ob and non-bridging Onb oxygen atoms change toward increasing Onb with addition of MgO content. The connectivity in the models has been studied and it is characterised by Q2 sites at metaphosphate composition, decreasing to Q1 sites upon the addition of MgO. The nearest neighbor distances of Mg-Mg and Na-Na in which modifier cations are bonded to non-bridging oxygens, Onb, are measured and show Mg-Mg correlations to be unfavorable in comparison to Na-Na correlations. In addition, Mg(Onb)N polyhedra are predominantly connected to each other by corner sharing.

Structure and luminescent properties of Sm3+-doped metaphosphate glasses

This paper investigates the effects of the phosphate network topology on the luminescent properties of mixed sodium/alkaline earths metaphosphate glasses doped with Sm 2 O 3 . The glasses were obtained using the melt quenching technique and analysed preliminarily by X-ray diffraction to confirm the vitreous nature of the samples. Raman spectroscopy, density, and thermal analyses were pursued to validate the persistence of metaphosphate chains and examine dopant-induced effects on the phosphate network. The fluorescence analyses of the glasses show the regular emission lines of Sm 3+ starting from the 4 G 5/2 energy level to the 6 H J/2 manifold with the largest transition in the red-orange part at 595 nm. An additional emission line starting from the higher excited state 4 F 3/2 to 6 H 5/2 between 520 and 540 nm was also detected with different intensities in all the studied compositions. This peculiar luminescence was correlated with the structure/topology of the glasses using the Judd-Ofelt theory together with the radiative and non-radiative properties of the host compositions. • The glass structure and properties did not change upon Sm 2 O 3 addition. • The changing topology of the glasses affects the luminescence of Sm 3+ . • The Ω 6 parameter indicate a very low vibrational amplitude of Sm 3+ -ligands bonds. • Defects related to NBO induce energy transfer to Sm 3+ ions.

Erratum for structural features of (Li,Na,K)PO3 mixed alkali metaphosphate glass for significant anisotropy

AbstractThe manuscript contains mistakes in the structure of the Q3 unit in Figure 1, the title and AR values in Table 3, and two sentences in Section 3.2. These errata acknowledge and correct the mistakes. The corrections do not lead to any changes in the discussion or conclusions.