康宁公司

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%.

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.

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.

Rotation of crystal seed during the early stages of growth around 3000 K $3000\mathrm{\nobreakspace K}$ in a glass matrix has been observed due to some torque, contradicting the expectations from the isotropic, uniform structure of the surrounding amorphous matrix. We establish an atomistic origin of this new phenomenon from molecular dynamics simulations using LiNbO 3 ${\rm LiNbO}_3$ and LiNbO 3 ${\rm LiNbO}_3$ - SiO 2 ${\rm SiO}_2$ glasses as model systems. Effectively, it arises due to non-uniform forces on the seed from the surrounding glass, which appears inhomogeneous and anisotropic on the scale of glass-crystal interface. The seeded crystal growth (SCG) at higher temperatures amplifies this effect due to enhanced atomic dynamics. Silica, when added to LiNbO 3 ${\rm LiNbO}_3$ glass, reduces the crystal growth rate due to increased viscosity and restricted atomic mobility across the growth interface, but has minimal effect on the crystal rotation. These findings challenge a general assumption that glass is an isotropic material, especially during the early stage of its crystallization, and provide insights for tailoring the microstructure of widely used glass-ceramics.