This study investigates the structural role of indium in aluminoborosilicate glasses designed for advanced transparent optical glass-ceramics. Using a comprehensive multi-spectroscopic approach, including nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), as well as infrared and Raman spectroscopy, combined with transmission electron microscopy (TEM) and differential scanning calorimetry (DSC), we examine the impact of indium oxide on the glass structure and its crystallization behavior, with comparisons to an analogous gallium-containing series. The results reveal the ambivalent structural role of indium in these complex glasses. Glasses with 2 mol% In2O3 enable controlled crystallization, while those with >= 3 mol% exhibit phase separation and spontaneous devitrification, reflecting on the solubility limit of In2O3. In stark contrast, the gallium series shows no such behavior. High-resolution XPS analysis of In 3d binding energies confirms that indium in the glass network has a coordination number lower than six and exhibits high covalent character, supporting findings from vibrational and NMR spectroscopy, which show that the addition of both indium and gallium reduces boron tetrahedral units. TEM mapping reveals preferential depletion of indium and aluminum from silicon-rich regions, consistent with nanoscale phase separation. Glass transition and packing density measurements further support the complex structural role and bonding characteristics of indium in these glasses. We propose that a high aluminum content (>10 mol%) stabilizes partially 4-coordinated indium and promotes local agglomeration of indium oxide, reducing the activation energy required for the crystallization even at indium oxide concentrations as low as 2 mol%.

The structural role of alkali modifiers (Li, Na, and K) in aluminoborosilicate glasses remains incompletely understood despite their widespread industrial use. Here, we investigate a series of glasses with compositions 20M2O-xB2O3-(20-x)Al2O3-60SiO2 (M = Li, Na, K; x = 5, 10, 15, with additional x = 0 and 20 for Na). Lithium-containing samples are prepared in duplicate using isotope-enriched compositions to enable isotopic-difference neutron diffraction. Solid-state NMR shows that ∼98% of Al is tetrahedrally coordinated, independent of alkali type, while the fraction of tetrahedral B increases with decreasing alkali-field strength and increasing B/Al ratio. Neutron total scattering data are analyzed by peak fitting of real-space correlation functions, using NMR-derived coordination numbers as constraints. Subtle variations in B-O, Si-O, and Al-O bond lengths are observed, and by the isotopic difference method, we find that the Li-O bonds exhibit an asymmetric bond length distribution and an increasing coordination number with increasing B/Al ratio. A similar trend is observed for the Na-O bonds, exploiting the improper difference method. These results provide new insight into how alkali modifiers influence the structure of aluminoborosilicate glasses, which will be helpful for establishing composition-structure-property relations.

Molybdenum (Mo) imposes strict loading limits in conventional borosilicate nuclear waste glasses due to the tendency of tetrahedral molybdate [MoO4]2- species to phase-separate and crystallize as alkali molybdates. Here, we demonstrate an unprecedented 13.96 wt % (7.51 mol %) MoO3 solubility in peraluminous sodium aluminoborosilicate glassesa ∼15× increase over their peralkaline counterparts. Using Raman spectroscopy, multinuclear and dipolar-correlation magic angle spinning nuclear magnetic resonance (MAS NMR), electron paramagnetic resonance (EPR), and scanning transmission electron microscopy (STEM)-energy dispersive spectroscopy (EDS), we reveal that Na-deficient, low optical basicity conditions stabilize octahedral MoO6 units, which polymerize into molybdite-like Mo-O clusters dispersed within the glass matrix. These Mo-rich clusters suppress the formation of depolymerized [MoO4]2- environments typically responsible for Na2MoO4 precipitation and instead promote the formation of Na2Mo2O7 as the saturation phase. Concurrently, Mo solubility drives the conversion of AlO4 - to higher-coordination AlO5 species, liberating Na+ that is subsequently sequestered in molybdate-rich domains. The combined evolution of Mo coordination, modifier redistribution, and network depolymerization provides a mechanistic basis for the markedly enhanced Mo solubility in peraluminous compositions. These findings establish new structural guidelines for designing aluminoborosilicate waste forms with substantially greater capacity to incorporate Mo-rich nuclear waste streams.

The transition to clean energy and sustainable technologies necessitates securing strategic materials, yet traditional land-based mining is increasingly unsustainable. Seawater holds immense potential as a mineral source, but its intricate ionic composition limits current extraction techniques. Here, we report a family of ion-exchangeable materials by grafting phosphate groups onto metal-organic framework glasses, followed by precise heat and aqueous treatments. This process introduces facile exchangeable ions and exposes active functional groups. The developed materials display progressively enhanced Mg2+/Ca2+ selectivity as solution complexity increases from binary and ternary mixtures to synthetic seawater. Across three different natural seawater samples, the optimized material achieves Mg2+ uptake of 7-10 mg g-1 and Li+ uptake of 2-3 mg g-1 within 10 min, highlighting high capacity and rapid kinetics under realistic conditions. Quantitative mechanistic analysis reveals that ion exchange contributes to 72% of the total uptake, while 28% arises from phosphate functional groups and pore surface interactions. This dual-mode sorption mechanism underpins the material's excellent selectivity and rate performance relative to a typical commercial resin. Our work thus presents a promising route for designing efficient adsorbents to extract valuable minerals from unconventional sources and help to secure the raw materials vital for a low-carbon future.

This study investigates the influence of alkaline earth and zinc oxide (RO = MgO, CaO, SrO, BaO, ZnO) modifiers on K*/Na* interdiffusion in Na-aluminosilicate glasses. Results show that glasses incorporating high cation field strength modifiers generally exhibit enhanced K*/Na* interdiffusion, attributed to an increase in the proportion of Na* ions participating in a structural role of charge compensator rather than network modifier. 23Na NMR and molecular dynamics simulations reveal that high field strength cations reduce the concentration of non-bridging oxygen atoms (NBOs) around Na*, thereby increasing ion mobility. However, in glasses where ([R2O]+[RO])/ [Al2O3] approximate to 1, high cation field strength modifiers promote the formation of 5-coordinated Al species, leading to increased network connectivity and reduced diffusivity. While low cation field strength modifiers allow Na* to dominate network-modifying sites, high cation field strength modifiers force Na* into charge-compensating roles, facilitating interdiffusion. These findings underscore the complex interplay between glass composition, modifier field strength, and network structure in controlling ionic mobility and interdiffusion behavior.

This study investigates the structural and mechanical effects of pressure-induced densification on metaluminous sodium aluminoborosilicate glasses across a broad compositional range. Using a combination of experimental methods-such as magic-angle spinning nuclear magnetic resonance (MAS NMR), microindentation, Brillouin light scattering, and refractive index measurements-and molecular dynamics (MD) simulations, the research explores how hot compression (1 GPa at the glass transition temperature, Tg) alters glass network connectivity, coordination states, and mechanical behavior. Results reveal that densification promotes the formation of highercoordinated aluminum (AlO5/AlO6) and boron (BO4) species, particularly in boron-rich glasses, without significant non-bridging oxygen (NBO) contributions. Instead, the emergence of triple-bonded oxygens facilitates these structural transitions. These changes lead to an increased density, atomic packing density, and hardness, while reducing molar volume and enhancing resistance to elastic deformation. However, the densified glasses display a trade-off in crack resistance due to reduced network flexibility. This work underscores the critical role of pressure in tuning structure-property relationships in functional glass systems, providing valuable insights for advanced applications in high-performance display and semiconductor substrates.

Establishing the structure-property relationships in multicomponent oxide glasses is highly challenging due to their inherent compositional and structural complexity. In this work, we present a topology-inspired structural decoding strategy to predict the structural impact on the properties of 45S5-based mixed alkali bioactive (MAB) glasses, a prototypical multicomponent system. Two novel topological descriptors, angular rigidity (gamma ac) and persistent homology matrix (PHm), are introduced to map the structure-property landscape in MAB glasses. In detail, gamma ac accounts for the spatial averaging of network distortions, quantitatively predicting properties associated with network reorganization, such as glass transition temperature and hardness. PHm evaluates the topological similarity between glass and crystalline phases, thereby characterizing the resistance of MAB glasses against crystallization (i.e., glass stability). Compared with conventional network analysis approaches, our two topological descriptors concurrently capture the higher-order nonlinear evolution of properties driven by the synergistic interplay between composition and cooling history. Importantly, these topological descriptors are derived solely from static glass structures generated via experimental measurements, suggesting potential utility for understanding diverse disordered materials. This work thus establishes a closed-loop framework that integrates synthesis, characterization, and predictive modelling for the specific 45S5-based MAB glass systems. The demonstrated ability to correlate topological features with distinct properties within this system represents a step towards the rational design of multicomponent oxide glasses.

In oxide glasses, titanium can exist in multiple oxidation states and coordination environments, yet the spectroscopic signatures of lower-coordinated Ti3+ species remain poorly understood compared with the extensively studied Ti3+ in octahedral environments. In this work, aerodynamic levitation was employed to remelt ultra-low expansion (ULE) titanosilicate glass under reducing atmospheres at temperatures exceeding 2000 °C to promote reduction of tetrahedral Ti4+ to Ti3+ while preserving the intrinsically low coordination of titanium in the glass network. To establish coordination-dependent spectroscopic trends, highly polymerized Ti-doped sodium alumino/boro-silicate glasses were prepared under strongly reducing conditions by a conventional melt and quench process as model systems, while a sodium-titano-alumino-phosphate glass containing predominantly octahedral Ti3+ was used as a reference. All glasses were investigated using UV-Vis-NIR absorption, electron paramagnetic resonance (EPR), and Raman spectroscopy, complemented by density functional theory (DFT) and linear response time-dependent DFT (LR-TDDFT) computational predictions. The octahedral Ti3+ reference glass exhibits the characteristic absorption band near 523 nm and a nearly isotropic EPR signal around giso ≈ 1.92-1.94. In contrast, the reduced aluminosilicate and borosilicate glasses develop broad near-infrared absorption bands extending from ∼700-1500 nm together with EPR resonances containing high-g components approaching or exceeding g = 2.0, indicating substantial populations of lower-coordinated Ti3+ species. The reduced levitated ULE glass exhibits a dominant absorption band near 1085 nm and a rhombic Ti3+ EPR signal (gx ≈ 1.997, gy ≈ 1.942, gz ≈ 1.912), consistent with a low-symmetry and highly distorted octahedral and lower-coordinated environment. Collectively, these results provide new insight into the UV-Vis-NIR, EPR, and Raman structural characteristics of Ti3+ in different coordination environments and represent one of the first systematic efforts to distinguish lower-coordinated Ti3+ species from octahedral Ti3+ in oxide glasses.

Crack initiation and growth limit the mechanical reliability and industrial applications of oxide glasses. The conversion of glasses into glass-ceramics can help to compensate for this shortcoming, as the presence of crystals can cause crack deflection and crack bridging and then increase the fracture toughness. However, due to the different thermal expansion of crystal and glass phases, the generation of residual stress is inevitable, which will induce compressive or tensile stress in glass-ceramics, thus changing the crack propagation path and crack initiation resistance. As such, it is a challenge to simultaneously improve the fracture toughness and crack initiation resistance. In this work, we attempt to address this challenge by modifying the crystal content in Nb2O5-doped magnesium aluminoborate glass-ceramics to improve crack resistance. Due to the generation of Al4B2O9 crystals with a lower coefficient of thermal expansion compared to the glass matrix, compressive stress is generated on the surface of the glass-ceramics, which reduces the cracking probability. At the same time, the presence of crystals causes crack deflection and crack bridging phenomena, enhancing the fracture toughness. In addition, heat-treatment also leads to an increase in the network connectivity of the glass ceramics, contributing to the improvement of its overall mechanical properties.

Rare earth aluminate glasses are potentially useful for optical, luminescence, and laser applications. As reluctant glass formers, these materials exhibit unconventional atomic structures. To better understand how their structures correlate with glass formation, we investigate two rare earth aluminum garnet melts, La3Al5O12 (LAG) and Yb3Al5O12 (YbAG), which represent the relative extremes of good and poor glass forming ability in rare earth aluminates. Structural models have been refined to high-energy X-ray diffraction data over 1340-2740 K. Both melts contain mixtures of AlO4, AlO5, and AlO6 polyhedra, with larger fractions of [5]Al and [6]Al in YbAG. Extrapolation of the Al-O coordination distributions to the glass transition match closely with 27Al nuclear magnetic resonance measurements of (La1-zYz)3Al5O12 glasses, z = 0 to 1. During cooling, the mean coordination numbers increase for La-O in LAG from 6.45(8) to 6.98(8) and for Yb-O in YbAG from 6.02(8) to 6.21(8). Linkedness among Al-O polyhedra at ∼2450 K is mostly corner-sharing, with 9% edge-sharing in LAG and 19% in YbAG. Among [4]Al units, both melts have 6% edge-sharing that convert to all corner-sharing upon cooling. Network connectivity is compared using a newly defined metric, Kn, that is similar to the Qn distribution but that accounts for the edge-sharing and triply bonded oxygen present in these melts. The lower glass forming ability in YbAG as compared to LAG correlates with more edge-sharing, associated with the larger fractions of [5]Al and [6]Al, and lower connectivity among [4]Al units.

Lead borate glasses in the system xPbO-(100-x)B2O3 have been prepared in platinum and alumina crucibles. Glasses were investigated qualitatively by Raman and infrared spectroscopies, and quantitatively by NMR spectroscopy, to determine the effect of Al2O3 contamination on the glass network. Glasses melted in a platinum crucible had a formation range of 30 <= x <= 80 mol% PbO, while glasses prepared in alumina crucibles experienced an expansion in the formation range, i.e. 20 <= x <= 85 mol%, as a result of Al2O3 contamination from the alumina crucible. Both the mid-frequency Raman and infrared data, as well as NMR spectroscopy, suggest that the introduction of Al2O3 within the glass results in the under-modification of the borate network due to the formation of anionic AlOntype units charge balanced by Pb2+ ions. This is also reflected in the low-frequency region of the Raman and infrared spectra, which relates to the Pb-O vibrations, where the Pb-O bonding remains predominately ionic for a larger composition range in the Al2O3 contaminated glasses (x <= 60), while the Pb-O bond also acquires covalent character for x >= 70 mol%.

Power scaling of fiber lasers and amplifiers is currently limited by nonlinear optical effects, such as transverse mode instability (TMI) and stimulated Brillouin scattering (SBS). Addressing optical nonlinearities through a material approach allows for such challenges to be confronted at their source- the interaction of the light and the material, lessening the need for complex fiber designs. However, effectively mitigating these issues through compositional engineering requires considerably higher dopant concentrations than are now typical for the modified chemical vapor deposition (MCVD) derived silicate glasses from which modern commercial laser fibers are made. Fibers doped with high concentrations of P2O5 and B2O3 experience additional fabrication challenges, including draw-induced refractive index changes. Reported herein are index changes of up to six milliunits from this system, compared to index changes of fractions of a milliunit common in industry-standard compositions. More specifically, a passive borophosphosilicate fiber with a core composition of approximately 10 wt.degrees lo P2O5 and 15 wt.degrees lo B2O3 is investigated to determine the potential sources of these index changes. These investigations include explorations of glass topology by NMR and Raman spectroscopy, as well as the first direct evidence of the formation of boron phosphate (BPO4) linkages in MCVD optical fibers. (c) 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

The structure of titanium phosphate glasses (TiO2)x(P2O5)1-x with 0.70 ≤ x ≤ 0.75 was investigated by combining neutron and high-energy x-ray diffraction with solid-state 31P nuclear magnetic resonance (NMR) and Raman spectroscopy. The results were interpreted with the aid of an analytical model that delivers the composition dependence of the structural motifs. The structure of these materials was also simulated using ab initio molecular dynamics. A detailed 31P magic-angle spinning (MAS) NMR lineshape analysis, aided by the results obtained from double-quantum coherence spectroscopy, indicates the presence of P-O-P-connected network forming units at a level decreasing from 23% to 11% with increasing x. The diffraction results show a Ti-O coordination number of 5.32(7) at x = 0.715 that increases to 5.49(7) at x = 0.750. The findings demonstrate the prevalence of five- and six-coordinated titanium atoms and the coexistence of both two-coordinated oxygen atoms, O(II), and three-coordinated oxygen atoms, O(III). The Ti-centered polyhedra contribute to a network in which the phosphate groups form P-O(II)-Ti and P-O(III)-2Ti connections, with signatures that are evident in the 31P MAS NMR spectra. The results suggest that structural variability is a key factor in promoting vitrification in this atypical glass-forming system. The findings provide a benchmark for investigating the structure of other glass-forming materials based on networks of higher-coordinated polyhedral units.

Elucidating the intricate structures of novel bioactive glasses is essential for understanding their structure–property relationships, particularly regarding dissolution rate and bioactivity which are key factors in designing glass compositions for biomedical applications. In this study, we investigate the structure and property relations of a series of novel bioactive phosphosilicate glasses through an integrated experimental and computational study by using characterization techniques such as magic angle spinning nuclear magnetic resonance (MAS NMR), neutron diffraction, and molecular dynamics (MD) computer simulations. Our results reveal that zirconia significantly alters the chemical environment surrounding silicon, as evidenced by 29 Si NMR, through the formation of Si–O–Zr linkages. This structural modification is further supported by shifts in partial pair distribution function peak positions toward longer distances for P–O and Si–O pairs, as observed in neutron diffraction data for glasses containing 4 mol% ZrO 2 . Additionally, apparent depolymerization is observed around silicon, showing a decrease of Si Q 4 and Q 3 species with increasing ZrO 2 . Phosphorus predominantly exists as Q 0 (∼90%) and Q 1 (∼10%) species, showing little sensitivity to zirconia composition variations, as demonstrated by 31 P NMR. Increasing the P 2 O 5 content results in a more disordered and heterogeneous glass network, as neutron diffraction revealed. MD simulations indicate a preferential distribution of isolated orthophosphate units. The structural information from MD was employed to establish a quantitative structure–property relationship analysis with key physical properties, such as Young's modulus and density. These combined results highlight the power of integrating experimental and computational methods to unveil significant composition‐driven modifications in short‐ and medium‐range glass structures, ultimately governing the properties of bioactive glasses.

Copper-containing hydroxyapatite (CuHA) is hypothesized to be an effective approach to hinder orthopedic infection. Copper (Cu) is well regarded for its antibacterial potential yet remains understudied in bioceramics. Herein, a series of CuHA were evaluated by probing the Cu2+ ion using electron paramagnetic resonance (EPR). Additionally, particle size, surface area, and crystallinity measurements were performed. CuHA was heat-treated to form Cu-containing biphasic calcium phosphate (CuBCP), which enabled Cu release in aqueous solution to reach a maximum of 0.108 + 0.004 mg/L per 1m2 powder compared to its CuHA counterpart, which showed no Cu release per 1m2 powder. Agar diffusion and time-based bacterial broth analyses were conducted against gram-positive and gram-negative strains of bacteria for CuHA and CuBCP with results indicating potential bacteriostatic effects. The material that released the highest amount of Cu into aqueous solution also exhibited the largest inhibitory effect against S. Aureus (broth analyses) indicating a potential correlation.

Volatile anions such as chloride (Cl-), fluoride (F-), and sulfate (SO42-) play crucial roles in determining the behavior of silicate melts across geologic, industrial, and nuclear waste vitrification systems. Their incorporation affects the melt structure, phase stability, and processing properties, often through complex interactions with modifying cations. In nuclear waste vitrification specifically, volatiles play a significant role in inducing salt formation, a waste-loading-limiting phenomenon deleterious to melter operations and waste form durability. Here, model Hanford Site Low Activity Waste peralkaline aluminoborosilicate glasses were synthesized with Cl or F additions, alongside fixed SO42- content. These glasses were examined with a combined spectroscopy-microscopy approach that included electron microscopy and dispersive X-ray spectroscopy, Raman spectroscopy, NMR spectroscopy, and X-ray nano-Computed Tomography. Cl incorporation saturated at ∼3 mol %, beyond which excess halide and SO42- partitioned to a NaCl-rich molten salt. This salt formation reduced Na2O and SO42- content in the glass and increased the glass transition temperature (Tg), molar volume, 4-coordinated boron (N4), and network polymerization. By contrast, F was retained up to ∼12 mol % before liquid-liquid phase separation, leading to submicron-scale crystallization of CaF2, and with subsequent F addition, villiaumite (NaF) and cryolite (Na3AlF6). Before phase separation, F addition decreased Tg and increased N4. F had minimal effect on SO42- retention prior to crystallization, although SO42- preferably segregated into F-rich droplets after fluoride saturation.

Successful decoding of structural descriptors controlling the crystallization in multicomponent functional glasses can pave the way for the transition from the trial -and -error approach and empirical modeling for glass/glassceramic composition design toward more rational and scientifically rigorous Quantitative Structure -Property Relationship (QSPR) based models. However, due to the compositional and structural complexity of multicomponent glasses and the longer time and length scales associated with nucleation, the development and validation of QSPR models are still in it's infancy. The work presented in the article is an attempt to leap forward in this pursuit by combining the strengths of experimental and computational materials science to decode the chemo-structural drivers that promote or suppress nucleation and crystal growth in alkali/alkaline-earth aluminoborosilicate glasses leading to the development of a QSPR-based model (powered by MD simulations). The results reveal the following two descriptors that govern the nucleation and crystallization of a particular aluminosilicate phase in the functional glasses: (1) degree of mixing between the SiO4 and AlO4 units, i.e., Si-O-Al linkages, and (2) difference/similarity between the short -to -intermediate range ordering in the glass structure to that of the structure of corresponding crystalline phase. Based on the established composition-structure-crystallization behavior relationships, a cluster analysis based QSPR model has been developed (and tested) to predict the propensity of nepheline (and anorthite) crystallization in the investigated glasses. The model has been tested on several compositions from the present and previous studies and has successfully predicted the crystallization propensity of all glass compositions, even in cases where previous empirical and semi -empirical models were unsuccessful.

The work presented in this review combines the strength of experimental and computational materials science to understand the iron-induced structural rearrangements in peralkaline aluminoborosilicate glasses and their impact on the solubility of sulfur (as SO42-) in model nuclear waste glasses. The majority (>= 96%) of iron exists as tetrahedrally coordinated Fe3+ (both isolated and clustered) in the investigated glasses, thus acting as a network former being charge-compensated by Na+, while the remaining iron exists as tetrahedrally (distorted) coordinated Fe2+. Increasing Fe2O3 concentration (from 0 to 3 mol %) leads to glass network repolymerization through two mechanisms: (1) scavenging of Na+ by FeO4- units for charge compensation, likely from the nonbridging oxygen (NBO) sites, and (2) formation of Fe-O-(Si, B) linkages. Due to the decreased availability of NBO-associated Na+ in the glassy matrix with increasing Fe2O3 content, sulfur solubility diminishes as SO42- struggles to compete effectively with AlO4-, BO4-, and FeO4- for preferential charge compensation by Na+. Mossbauer spectroscopy reveals an insignificant impact of sulfur on the redox behavior or environment of iron in the glass structure, and SO42- prefers to be charge-compensated by Na+ over Fe2+

The structure of calcium aluminosilicate glasses (CaO)(x)(Al2O3)(y)(SiO2)(1-x-y) with the near tectosilicate compositions x similar or equal to 0.19 and 1 - x - y similar or equal to 0.61 or x similar or equal to 0.26 and 1 - x - y similar or equal to 0.49 was investigated by in situ high-pressure neutron diffraction and Al-27 nuclear magnetic resonance (NMR) spectroscopy. The results show three distinct pressure regimes for the transformation of the aluminum coordination environment from tetrahedral to octahedral, which map onto the deformations observed in the production of permanently densified materials. The oxygen packing fraction serves as a marker for signaling a change to the coordination number of the network forming motifs. For a wide variety of permanently densified aluminosilicates, the aluminum speciation shares a common dependence on the reduced density rho ' = rho/rho(0), where rho is the density and rho(0) is its value for the uncompressed material. The observed increase in the Al-O coordination number with rho ' originates primarily from the formation of six-coordinated aluminum Al(VI) species, the fraction of which increases rapidly beyond a threshold rho '(thr)similar to 1.1. The findings are combined to produce a self-consistent model for pressure-induced structural change. Provided the glass network is depolymerized, one-coordinated non-bridging oxygen atoms are consumed to produce two-coordinated bridging oxygen atoms, thus increasing the network connectivity in accordance with the results from O-17 NMR experiments. Otherwise, three-coordinated oxygen atoms or triclusters appear, and their fraction is quantified by reference to the mean coordination number of the silicon plus aluminum species. The impact of treating Al(VI) as a network modifier is discussed. (c) 2024 Author(s).