Bond counting strategies provide a simple but robust methodology for examining the connectivity of the network forming motifs in oxide glasses. This utility is demonstrated for several case examples in which diffraction is combined with solid-state nuclear magnetic resonance and other methods to probe the glass structure. The approach is used to show that four-coordinated Zn²⁺ and Mg²⁺ ions act as network modifiers in alkali bearing metasilicate glasses. Analytical models are then derived for the structure of mono- or di-valent cation containing aluminosilicate glasses in which the fraction of six-coordinated Al³⁺ ions is negligibly small and the other aluminium species are regarded as network formers. The results lead to an assessment of the network modifying versus charge compensating roles of the Zn²⁺ and Mg²⁺ ions. Next, the effect of high-pressure on the network connectivity of aluminosilicates is investigated, leading to a quantification of the fraction of triply bonded oxygen atoms (or oxygen triclusters) in fully polymerised structures. A network forming role is then found for six-coordinated Nb⁵⁺ ions in the binary Nb₂O₅–NaPO₃ system. Finally, it is noted that the oxygen packing fraction acts as a marker for structural change in network-forming oxides under high-pressure conditions. The findings illustrate the power of the bond-counting methodology in elucidating the structure of amorphous oxides and show the rich diversity in framework structures that originates on progressing from a Zachariasen viewpoint of oxide networks.

Intermediate-range order in glasses is essential for understanding their structural features but remains elusive due to a lack of periodicity. We review recent advances using experimental and virtual angstrom-beam electron diffraction methods to directly probe local atomic configurations. Our approach reveals pseudo-periodic arrangements of columnar structures that give rise to the first sharp diffraction peak, linking reciprocal-space features to underlying real-space structures. In addition, our recent data obtained from molecular dynamics simulations support and extend our previous findings. The importance of viewing direction and the origin of the shape of the FSDP are also discussed.

The construction of large quantum beam facilities such as the synchrotron radiation facility SPring-8 and the high-intensity proton accelerator facility J-PARC has provided access to high-intensity, high-energy quantum beams that are essential for structural analyses of non-crystalline materials via diffraction measurements in Japan. The developments of quantum beam diffraction techniques led to significant advancements in the research field. By the complementary use of X-rays, which are sensitive to heavy elements, and neutrons, which are sensitive to light elements, along with the advances in computer simulations and topological analysis techniques, we have achieved a deep understanding of disordered structures with intermediate-range ordering. In this article, we review the recent results obtained by the complementary use of quantum beam diffraction and topological analyses of silica polymorphs, covering silica crystals and densified silica glasses. The comparison between the persistent homology analysis data and the ring size distribution has led to the classification of a series of densified silica glasses and crystals in terms of ring persistency (ring shape) and ring entropy (topological order–disorder). This is a new concept to understand the nature of order–disorder observed in a series of silica polymorphs without using diffraction data. We also discuss the differences among disordered materials, which comprises an AA₄ (A = Si) tetrahedral network (amorphous silicon), an AX₄ (A = Si, X = O) tetrahedral network (glassy silica), and a non-tetrahedral network due to isolated AX₄ (A = C, X = Cl) tetrahedra (liquid carbon tetrachloride) in terms of the origin of a three-peak structure, FSDP (Q₁), PP (Q₂), and Q₃.

Poly(vinyl alcohol) (PVA)-sulfuric acid (H₂SO₄)-lithium trifluoromethanesulfonate (LiOTf) hydrogel polymer electrolytes (HPEs) were prepared by solution casting method. Upon the adulteration of 10 wt.% LiOTf, the ionic conductivity of HPE improves from (9.71 ± 0.04) × 10⁻³ S cm⁻¹ to (1.06 ± 0.01) × 10⁻² S cm⁻¹ at ambient temperature. The glass transition temperature (T_g) of HPE is low compared to pristine PVA, as shown in differential scanning calorimetry (DSC) analysis. The XRD analysis had shown decreased degree of crystallinity upon addition of 10 wt.% of LiOTf. Linear sweep voltammetry (LSV) shows an improvement in potential window from 1.5 to 3.12 V, while transference number proves the ions are the main conduction contributor. An electric double layer capacitor (EDLC) was assembled. The EDLC fabricating using the most conductive HPE exhibits a higher specific capacitance of 18.5 F g⁻¹, as illustrated in CV analysis. The fabricated EDLC demonstrates its specific capacitance of 44 F g⁻¹, energy density of 5.4 Wh kg⁻¹ and power density of 293.8 W kg⁻¹ with above 90 % of coulombic efficiency in GCD analysis.

Li_xLa_(1−x)/3NbO₃ with an A-site-deficient perovskite structure was investigated with a focus on the relationship between its atomic configuration and Li⁺ diffusion properties. To this end, total scattering (diffraction) measurements were performed, and then reverse Monte Carlo modeling using the data was employed to construct the atomic configuration. The results suggest that the partial occupancy of La in the La-poor layer facilitate Li⁺ diffusion across the layer owing to the volume contraction. Furthermore, topological analyses conducted via persistent homology using the constructed atomic configuration indicate that a large fourfold ring formed by Nb and O is one of the reasons for superior Li⁺ diffusion in Li_xLa_(1−x)/3NbO₃.

Silica-water liquid mixtures become completely miscible above the critical point. The resulting temperature–pressure quenched hydrous glasses, containing 8 and 12 wt.% H₂O, have been modeled using Empirical Potential Structural Refinement based on high energy X-ray diffraction data to give representative atomic arrangements. For these compositions, winding chains and rings of SiO₄ tetrahedra, surrounding clusters of water, are found to preserve the local atomic arrangement of silica as well as the intermediate range order, indicated by the persistence of the first sharp diffraction peak. Our models show that ∼7 % of oxygen atoms within the silicate network are replaced with hydroxyl molecules. These hydroxyls form silanol groups that effectively act as non-bridging oxygens to depolymerize the silicate network. Despite this, the ring size distribution remains very similar in the hydrous glasses to that of dry SiO₂ glass. The resulting structures are found to be heterogenous over the atomic to nanometer length-scale, with the effective void space due to the cavities increasing by 8–21 % compared to dry silica. Trapped water molecules within the silicate network form moderately strong hydrogen bonds with the silanols in isolated cavities and pockets at a concentration of 8 wt.% water. At 12 wt.% water in SiO₂, more water–water hydrogen bonds form within the cavities, along with water molecules residing in non-bonded interstitial locations, although the number of water molecules bonded to silanols within the silica network remains unchanged.

We fabricated glass-ceramics (GCs) crystallized with ZnO by utilizing an alumino-borosilicate glass rich in ZnO as a precursor. We hypothesized that SnO addition into the precursor glass could control the formation of Zn-enriched regions, stemming from nanometric inhomogeneities. This study explores the relationship between the amount of SnO and the morphology of the ZnO phase. The addition of SnO led to the crystallization of rod-shaped ZnO whose dimensions decreased significantly with increased SnO content. Microscopic observations indicated a reduction in the size of the Zn-enriched regions due to SnO addition, confirming the controllability of the crystallized ZnO phase’s morphology/size. We also examined the photoluminescent properties of the resulting GCs.

The physical and structural parameters of glass depend on its preparation conditions. Fictive temperature, T_f, is a standard for glass obtained from the super-cooled liquid. Although the T_f value is discussed from the viewpoint of structural relaxation defined by infrared vibration, there should be structural correlations at the longer ranges, which are worthy of exploration. Here, we demonstrate the structural change of the intermediate range in SiO₂ glasses with different T_f values using X-ray and neutron diffraction, inelastic light scattering, and positron annihilation spectroscopy. By annealing the SiO₂ glasses, i.e., decreasing T_f, an increase in the first sharp diffraction peak (FSDP) heights and narrowing of the peak width are observed. Differential structure factor ΔS(Q) of neutron diffraction reveals a formation of the thermally derived O–O inter-tetrahedral correlation in high-T_f glass. Spectroscopic analyses (Raman scattering, stimulated Brillouin scattering, and positron annihilation spectroscopy) suggest that a certain structural change has occurred in the SiO₂ glass exhibiting higher T_f values, confirming that these approaches can be used as probes for structural ordering. Considering ΔS(Q) of neutron diffraction, it is suggested that the structural changes in SiO₂ glass with higher T_f values observed by spectroscopy correlate with oxygen-related structural change in the intermediate range. Since the observed structures of each analysis are different, these multiscale and quantitative examinations are important for precise examination of various random materials.

B₂O₃ glass is a non-tetrahedral network-forming glass whose structure consists of boroxol rings that cannot form in crystalline phases under ambient conditions. In this study, a three-dimensional structural model of B₂O₃ glass containing a large fraction of boroxol rings (∼80 %) was successfully constructed by reverse Monte Carlo (RMC) modeling on the basis of high-energy X-ray diffraction data. This achievement is notable given that maintaining such a large fraction of boroxol rings has traditionally been considered difficult in conventional RMC modeling. Analyses of coordination number, bond angle distributions, and ring size distribution confirmed that the boroxol rings were well preserved in the model. The ring size distribution and persistence diagram revealed that B₂O₃ glass contains a large fraction of boroxol rings and a small fraction of larger rings with exceptionally high topological order, compared with typical tetrahedral network-forming glasses such as SiO₂ glass. Our modeling and topological analysis can be extended to various B₂O₃-based glasses to provide a firm basis for understanding their physicochemical and structural properties at the atomic level.

Amorphous alumina (Al₂O₃) is an essential oxide material with widespread applications in electronics, catalysis, and coatings, where its properties are critically influenced by structural disorder and defects. Unlike crystalline phases, amorphous alumina cannot be formed by melt-quenching but can be synthesized through other non-melting routes, often yielding a high fraction of AlO₅ units that determine its functionality. In this study, we systematically examined how heating conditions, post-treatment atmospheres, and storage history affect defect formation and optical responses in amorphous alumina. XRD confirmed that all samples remained amorphous after heating or post-treatment. ESR and UV–Vis analyses revealed that heating at 600–800 °C generated unidentified ESR signals near g = 1.97, whereas rapid heating and quenching induced g = 2.003 signals associated with oxygen-defect-related paramagnetic centers that correlated with reduced reflectance and gray coloration. Prolonged precursor storage further enhanced these signals, highlighting the sensitivity of defect states to sample history. Post-treatments produced atmosphere-dependent defects: air and oxygen generated some unidentified ESR signals, affecting UV–visible reflectance, while ozone generated unusually strong ESR peaks at g = 2.01–2.02, resembling O₃· and Al–O· radicals, which remained stable for months but primarily influenced UV absorption. Long-term storage of amorphous alumina led to the appearance of weak ESR signals and gradual increases in high-g-value signals, although reflectance remained nearly constant. Absorption spectra showed distinct peaks between 3–5 eV depending on the defect species and treatment atmosphere, emphasizing the strong coupling between defect chemistry and optical behavior. Overall, these findings demonstrate that the defect states of amorphous alumina are not fixed by intrinsic local structure alone but are governed by thermal history, treatment atmosphere, and storage conditions. The observed correlations between ESR signals and optical spectra provide fundamental insights into the defect chemistry of amorphous alumina, offering guidelines for tailoring its properties in optical, dielectric, and catalytic applications.

The density and ultrasonic velocities of a commercial alumino-borosilicate glass were measured under hydrostatic compression; pressure-induced structural changes were investigated by in situ high-pressure Raman spectroscopy. Density increased with pressure, showing an increasing compressibility up to ∼5 GPa. At higher pressures, up to ∼12 GPa, the compression behavior became more nearly monotonic. Both the longitudinal and transverse acoustic velocities exhibited a clear negative pressure dependence up to 5–6 GPa—the so-called acoustic anomaly. Consistently, the bulk modulus showed a negative pressure dependence up to around 6 GPa, indicating an elastic anomaly. Raman spectra at low pressures suggest that densification proceeds primarily by simple contraction of network rings (e.g., six-membered rings), corresponding to elastic deformation of the glass network. Above ∼5 GPa, signatures of three-membered ring formation emerge, implying that larger rings collapse and reorganize into smaller ones once the elastic limit is exceeded. Indeed, glasses recovered from pressures ≥5 GPa retain enhanced Raman scattering attributable to three-membered rings.

Durability of hierarchically porous silica monolith columns against strong acid and alkali aqueous solutions was examined under flow-through conditions relevant to cleaning-in-place (CIP) as a cleaning method. Silica monoliths were exposed to strong acids, including aqua regia, and strong alkaline solutions of sodium hydroxide, followed by controlled rinse/neutralization protocols. Under flow-through washing, the monoliths showed no significant degradation in pore structural parameters after strong acid and alkaline treatments over a short time period. Alkaline CIP in 0.01 M or 0.1 M NaOH treatment induced systematic pore-parameter changes consistent with silica leaching during flow, while the retained bulk structure of silica monolith was confirmed. The observed pH breakthrough curves of a two-step neutralization behavior were attributed to the sequential deprotonation of surface silanol groups. In contrast, high-concentration alkaline exposure without post-treatment neutralization caused residual Na species and surface coarsening. These results show that the pore structure of bare silica monolith during alkaline CIP is altered depending on alkali concentration, effective contact time, and post-treatment neutralization, which serves as a reaction-quenching mechanism. These findings are useful in the regeneration of the silica monoliths for repeated use.

The tungsten oxide Magnéli phase, W₁₈O₄₉, is a promising material for thermoelectric (TE) applications due to its high electrical conductivity, σ, and relatively low thermal conductivity, κ. To improve the TE performance, the Seebeck coefficient, S, should be increased by lowering the electron carrier concentration. In this study, we attempted to substitute a lower-valence cation, V⁴⁺/V⁵⁺, for W⁵⁺/W⁶⁺ in W₁₈O₄₉. The V-doped samples were synthesized by reacting W₁₈O₄₉ and VO₂ (V⁴⁺) or V₂O₅ (V⁵⁺) according to the cation ratio, W_1−xV_x (x = 0, 0.05, 0.10, 0.15), followed by spark plasma sintering. The V-doped samples exhibited lower σ and larger S compared to the pristine sample, indicating the reduction in the carrier concentration. The doping effect is more pronounced for the V₂O₅ dopant, leading to the enhancement of the power factor, σS², to 0.73 mW K⁻² m⁻¹. The V doping resulted in the reduction of not only the electronic contribution but also the lattice contribution to κ. The latter result is likely due to the phonon scattering by point defects at the W/V sites and the grain boundaries between the W₁₈O₄₉-based phase and secondary phases caused by the substitution. The highest dimensionless figure of merit, ZT, of 0.22 at 1073 K was achieved for the x = 0.10 sample with the V₂O₅ dopant.

The structures of the main component (K,Na)NbO₃ (KNN) in a lead-free piezoelectric ceramic 0.97[(K_0.48Na_0.52)_0.82Ca_0.04Li_0.02Nb_0.85O_3−δ]–0.03[K_0.85Ti_0.85Nb_1.15O₅]–x[MnO₂, BaCO₃] (x = 0.00, 0.01, 0.015, 0.02, and 0.03) have been investigated with synchrotron powder X-ray diffraction and transmission electron microscopy measurements. The structural symmetry of the KNN phase has shown the P4mm in the X-ray diffraction data of all samples from x = 0.00 to 0.03. The Mn-rich clusters of 10–50 nm size in KNN phase have been observed by energy dispersive X-ray spectroscopy element mapping images at x = 0.02. The Mn-rich clusters with the same crystal structure as KNN are dispersed in the KNN matrix with rotational relationship of the coincidence site lattice Σ = 5. The x = 0.02 sample has shown the high piezoelectric properties of piezoelectric constant d₃₃ = 140 pC/N, electromechanical coupling coefficient k_p = 0.42, dielectric constant ε₃₃^T/ε₀ = 750, and mechanical quality factor Q_m = 650.

All-solid-state sodium batteries are gaining attention because they are safe, use abundant sodium resources, and are promising candidates for future energy storage applications. Sodium iron sulfides are suitable positive electrode active materials because of their high theoretical capacity and use of low-cost elements. In this study, the electrode properties of Na₆FeS₄ and Na₇Fe₂S₆ in all-solid-state cells were evaluated in comparison with those of Na₂FeS₂ and Na₅FeS₄. Na₆FeS₄, Na₅FeS₄, Na₇Fe₂S₆, and Na₂FeS₂ were synthesized by ambient-pressure heat treatment using sodium polysulfides. The all-solid-state cells using Na₆FeS₄ and Na₇Fe₂S₆ as positive electrode active materials exhibited initial charge capacities close to their theoretical capacities and operated reversibly with high capacities of over 400 mAh g⁻¹, exceeding the capacity of Na₂FeS₂. This study contributes to the development of low-cost and high-capacity positive electrode active materials for all-solid-state sodium batteries.

The electronic structure and optical properties of Mn-doped Ba₃V₂O₈, a promising cobalt-free pigment, are investigated using first-principles calculations to elucidate the microscopic mechanism of its vivid blue coloration. Structural optimization done by the pseudopotential method, combined with high-precision all-electron band calculations (FLAPW method) reveals the interplay between local lattice distortion and optical response. The results demonstrate that the substitution of V⁵⁺ with Mn⁵⁺ (3d²) introduces spin-polarized impurity states within the band gap. These mid-gap states arise intrinsically from the crystal field splitting of the Mn orbitals into occupied e and unoccupied t₂ levels. Crucially, the [MnO₄]³⁻ tetrahedra undergo significant structural distortion, lowering the local symmetry from T_d to C₁. While this distortion is not the primary origin of the impurity levels, it plays a decisive role in governing the optical transition probabilities. The symmetry breaking enhances the hybridization between Mn 3d and O 2p orbitals, relaxing the selection rules for d–d transitions. Consequently, a distinct absorption peak arises at approximately 1.6 eV, which is responsible for the blue color, alongside a charge-transfer transition around 3.3 eV. Furthermore, the distortion induces strong optical anisotropy, manifested as a significant splitting of the dielectric function along the principal optical axes. This study provides a comprehensive theoretical framework linking the local geometric distortion to the intense and anisotropic optical response of Mn-doped Ba₃V₂O₈.

Sol–gel coatings of TiO₂/SiO₂ multilayers potentially control thermal radiation spectra from electric heaters, providing an energy-efficient solution. This study investigated sol–gel techniques to develop crack-free thick coatings that are crucial for infrared applications. Similar to many reports, the application of multiple thin coatings significantly enhanced fracture resistance. Residual stress measurements using Stoney’s method showed that the stresses in multiple coatings were comparable to those in single coatings despite their different critical cracking thicknesses. Based on the results, a specific fracture mechanism was proposed for the single coatings. Further coatings beyond the critical thickness resulted in delamination from the substrate. Pull-off tests showed that the adhesion between TiO₂ and glass was weakest among the TiO₂, SiO₂, and glass interfaces. To prevent delamination, a SiO₂ buffer layer was added to the TiO₂/glass interface, facilitating the formation of TiO₂ films with thicknesses of several micrometers. At high temperatures, surface roughening occurred owing to the grain growth of rutile TiO₂, which was prevented by applying a SiO₂ overcoat. A long-pass optical filter was fabricated using TiO₂/SiO₂ stacks with the buffer layer and overcoat, which effectively blocked the thermal radiation from a red-hot heater at wavelengths near 1 µm.

Carbon dioxide (CO₂) electrolysis is one of the promising technologies to convert CO₂ into value-added chemical compounds and has attracted attention in recent years from the perspective of energy crisis and carbon neutrality. For efficient CO₂ electrolysis, numerous attempts have been made to develop superior electrocatalysts that accelerate the CO₂ reduction reaction (CO₂RR), and their performance has been enhanced by controlling structure, morphology, and elemental composition. However, the effect of grinding treatment of catalysts on their structure, morphology, and CO₂RR activity is frequently underestimated, which is performed for grain refining of catalyst particles to achieve optimum activity in general. In the present paper, we focused on Zn–Al layered double hydroxide (LDH) as an electrocatalyst which has CO₂RR activity for carbon monoxide (CO) evolution. Zn–Al LDH and its ground samples for 10, 20, 30, and 60 min (Gx-LDHs, x = 0, 10, 20, 30, and 60, respectively) were prepared using a facile co-precipitation method and simple grinding with a mortar and pestle. Remarkably, Gx-LDHs exhibited superior activity for CO₂-to-CO conversion as grinding proceeded. In particular, the growth rate in partial current density of CO was 3.2-fold and 1.6-fold from G0-LDH (as-prepared) to G10-LDH and from G10-LDH to G60-LDH, respectively. XRD and TEM analysis showed that the crystal structure of Zn–Al LDH collapsed due to amorphization as grinding proceeded. XAFS analysis indicated that Zn sites in the amorphous phase are mainly in the low-valent Zn state (Zn^δ+, 0 < δ < 2), which is a favorable state for CO₂-to-CO conversion. Our results highlighted that grinding treatment clearly affected the structural and morphological properties of Zn–Al LDH, enhancing its CO₂RR activity.

A sustainable method for efficiently producing and depositing silver nanoparticles (AgNPs) onto cellulose nanofibers (CNFs) was developed in this study by harnessing high-pressure wet-type jet-milling-induced redox reactions. An aqueous solution of silver nitrate was mixed with a CNF suspension and subsequently subjected to 0–4 jet-milling passes at a discharge pressure of 200 MPa. Additionally, the influence of the pipe fitting material on the formation of nanoparticles (NPs) was evaluated by using either 304 stainless steel (SUS304) or brass pipe fittings between the feed tank and the collision chamber. The X-ray diffraction pattern of the sample prepared using brass fittings and subjected to one jet-milling pass exhibited distinct peaks corresponding to metallic silver, confirming the presence of AgNPs, in addition to those from cellulose crystallites. In contrast, the sample prepared using SUS304 fittings exhibited only peaks corresponding to cellulose crystallites, with no detectable peaks attributable to metallic silver. Transmission electron microscopy revealed that the CNF surface of the sample processed with brass fittings were uniformly and densely covered with spherical AgNPs (diameters <5 nm), and that the particle size distribution was remarkably narrow. In contrast, the quantity of NPs prepared using SUS304 fittings was insufficient to achieve uniform coverage, with deposition confined to isolated regions on the CNF surface. Furthermore, the larger amount of AgNPs deposited with the brass fittings, as compared to the SUS304 fittings, proportionally increased with the number of jet-milling passes. This enhanced deposition is attributed to the presence of copper and zinc in the brass fittings, which likely promote the redox reaction-induced reduction of silver ions. By synergistically coupling the intense cavitation generated during high-pressure wet-type jet-milling with redox activity derived from brass fittings, the reduction of Ag(I) to Ag was markedly enhanced, enabling dense and uniform deposition of AgNPs on the CNF surface.

Na₂FeP₂O₇ cathode materials for sodium-ion batteries were synthesized from NaH₂PO₄ and Fe₂O₃ raw materials using a simple solid-state synthesis method involving mechanical milling and calcination. Specifically, four types of active materials were prepared via carbon compositing with the calcined raw materials, followed by additional calcination. Electrode slurries were fabricated by adding conductive additives and binders to the active materials, which were then assembled into coin cells and evaluated through electrochemical tests. According to the results, the electrode that underwent the solid-state synthesis process, followed by carbon compositing and subsequent re-calcination, exhibited the highest diffusion coefficient. The discharge capacities measured at 0.1, 10, and 30 C-rates were 87.8, 59.8, and 15.9 mAh g⁻¹, respectively. The electrode also exhibited excellent capacity retention, maintaining 99.9 % of its initial capacity (81.6 mAh g⁻¹) after 200 cycles at 1 C-rate, demonstrating good battery performance.