Bismuth phosphate glasses possess remarkable properties such as a high refractive index (similar to 1.9), low characteristic temperatures, thermal stability against crystallization, and an appreciable transparency window spanning from ultraviolet (UV) to near infrared (NIR). These characteristics make them promising materials for optical devices and photonic applications. This study focuses on investigating the properties of a novel bismuth-rich phosphate glass system with a ternary composition of Bi(PO3)(3)-Bi2O3-Na2O. The synthesis was carried out using the conventional melt-quenching method in alumina crucibles under ambient air conditions. Structural and optical properties of the newly developed glass system were assessed using Raman and UV-Vis spectroscopies, differential scanning calorimetry (DSC), and P-31. and Na-23 nuclear magnetic single and double resonance. The P-31-NMR and Raman analysis reveal the depolymerization of the metaphosphate network with Bi2O3 and Na2O, acting as classical network modifiers with the theoretically expected conversion rates of three and one bridging oxygen per equivalent, respectively. The tendency of nanoparticle formation increases with the concentration of Bi2O3. UV-vis spectroscopy demonstrates that the values of the optical band gap are correlated with the modifier concentration. In addition, they indicate the formation of Bi-0 nanoparticles. Transmission electron microscopy (TEM) images identified nanoparticles of spherical shape, ranging from 4 to 70 nm in diameter. In summary, the results demonstrate a promising novel phosphate glass system containing high concentrations of bismuth atoms, with the potential for elemental Bi-0 nanoparticle formation.

The 25Mg nuclear magnetic resonance (NMR) spectroscopy of diopside (CaMgSi2O6) glass is revisited by comparing the data acquired at moderate (14.1 T) magnetic fields with literature data at ultrahigh (35.2 T) magnetic fields to probe the informational content of measured field dependent spectra. The glass structure was modeled using ab initio molecular dynamics (AIMD) and classical molecular dynamics (CMD) simulations using Pedone potentials. It shows a distribution of 4-, 5-and 6-coordinated magnesium atoms which yields an average Mg-O coordination number of 4.7 +/- 0.1 (AIMD) or 5.0 +/- 0.1 (CMD), close to that found from diffraction experiments. Density functional theory was then used to provide the nuclear magnetic resonance (NMR) parameters for the individual magnesium sites and the 25Mg magic angle spinning (MAS) NMR spectra were calculated accordingly. The results establish a 25Mg chemical shift scale as a function of the mean Mg-O distance but do not show a convincing correlation between the 25Mg isotropic chemical shift and the coordination number. They show that while ultrahigh field NMR significantly enhances the chances of detecting bimodal distributions, owing to the diminishing effect of line broadening by quadrupolar interactions, there will be ambiguity in the assignment and quantification of the features to different Mg coordination states. The findings are a prerequisite for establishing quantitative structure-property relations for Mg-bearing silicate glasses.

The scientific and technological interest in niobium-bearing materials has significantly increased in recent years. Still, reports on the structural details about the short- and medium-range order of the intermediate oxide Nb2O5 in glasses are quite scarce. In this work, the structural mechanisms underlying the incorporation of niobium oxide into lithium metaborate glass spanning concentrations up to similar to 25 mol % are investigated through standard and advanced solid-state nuclear magnetic resonance and Raman spectroscopies. The commonly encountered NbO6 distorted octahedral coordination occurs across the entire range of concentrations. With increasing niobia content, systematic changes in the speciation of the three-coordinated boron units are observed, revealing a progressive increase in the concentration of BO2/2O- groups. Furthermore, heteronuclear dipolar Li-7-Nb-93, and unprecedented B-11(III)-Nb-93 and B-11(IV)-Nb-93 recoupling experiments reveal an increase in all of the dipolar interaction strengths, reflecting the formation of B-O-Nb connectivities with increasing Nb2O5 content.. Above 10 mol % Nb2O5, the Raman spectra suggest the onset of niobium-oxide clustering. Altogether, these results suggest that niobium acts as a network former in alkali borate glasses, which is in consonance with the structural role reported for Nb2O5 in alkali silicate and phosphate glasses.

The structure of gallium-doped biosilicate glasses and glass-ceramics, prepared using the melting/cooling method, was studied by high-resolution multinuclear solidstate 29Si, 31P, 23Na and 71Ga NMR spectroscopy. 29Si MAS NMR spectra reveal the successive formation of Ga-O-Si linkages, as evidenced by a linear increase of the chemical shift measured for the center of gravity. 31P spectra reveal the dominance of orthophosphate units. Gallium is present predominantly in the four-coordinated state, forming GaO4/2-units requiring compensation by network modifier cations. These results confirm the role of gallium as a network forming species in this glass system. In this role, gallium serves to impart higher thermal and mechanical stability to the glasses, owing to the reduction of non-bridging oxygen atom concentrations. Crystallization of the glasses leads to the formation Na2CaSi2O6, NaCaPO4 and NaGaSiO4. While most of the silicon inventory largely crystallizes, the majority of the phosphorus species, along with some of the gallium species, remains in a residual vitreous form. Incomplete crystallization under the standard biosilicate crystallization protocols is particularly found for the Ga-containing glasses.

Magnesium and zinc are important additives or substituents in melt-quenched Na2O-CaO-SiO2-P2O5 bioactive glasses, due to their beneficial influence on glass stability and processability. They modify the dissolution kinetics of these glasses and impart favorable biological properties and functions to them. For rational bioactive glass design, it is essential to understand the local environments and distributions of these ions. While diffraction studies suggest MgO and ZnO to be close-to-four-coordinate in silicate glasses, their structural roles in the network are still under debate. Traditionally these oxides have been viewed as network modifiers, converting Si-O-Si linkages to anionic non-bridging oxygen atoms, whose charges are compensated by the divalent cations. It has been suggested that MgO4/2|(2-) or ZnO4/2|(2-) network-forming units (NFUs) may be present, forming Mg-O-Si or Zn-O-Si linkages. If such units are formed, they would attract modifier cations for charge compensation, which would in turn result in an increased degree of polymerization of the silicate species, the main network-forming component. This study explores the roles of MgO and ZnO in bioactive glasses with approximate composition 50SiO(2)-(50-x)[MO,M'O-2]-xP(2)O(5) in mol% (2 <= x <= 6), where M = Ca, Sr, Mg, Zn; M' = Na, K. Quantitative estimates of the various silicate and phosphate NFUs were obtained from Si-29 and P-31 solid-state nuclear magnetic resonance (NMR) spectroscopic techniques and molecular dynamics (MD) simulations, allowing the determination of the degree of network polymerization in terms of the average Si and P connectivities (-values). Both NMR spectroscopy and MD studies consistently revealed that the extent of Si polymerization increases, as expected, with P2O5 addition, reflecting the well-documented preferential cation attraction by the phosphate species. On the other hand, data obtained from a set of comparative samples containing either Mg, Zn, or a mixture of both showed no significant changes in the degree of silicate network polymerization. This result strongly supports a network-modifying role of both magnesium and zinc oxide, as suggested by previous works.

The structure of glasses in the aluminoborophosphate glass system with compositions 40Na2O-40P2O5-(20-x)Al2O3-xB2O3 (0 <= x <= 20) has been studied by single- and double-resonance solid-state nuclear magnetic resonance (NMR) spectroscopy. The principal network forming units (NFUs) were identified and quantified by high-resolution spectra obtained by magic-angle spinning (MAS) NMR. The boron atoms are predominantly four-coordinated, while the Al species occur in four-, five- and six-fold coordination, and their average connectivity increases with increasing boron content. The connectivities between these NFUs were determined by dipolar recoupling experiments such as 11B{31P} and 27Al{31P} rotational echo double resonance (REDOR) and 31P double-quantum filtering experiments. No significant 27Al-11B interaction was detectable. The results indicate a strong preference for Al-O-P and B-O-P heteroatomic connectivities, whereas a random linkage model clearly does not provide an appropriate description. The glass transition temperature shows a characteristic nonlinear compositional dependence on x, with a maximum near x = 10. This behavior can be modeled by considering the average connectivity density of the network, calculated from the NFU distribution as deduced from the quantitative connectivity analysis. 23Na MAS NMR and 23Na{31P} REDOR results indicate that the sodium ions maintain a constant local environment dominated by the phosphate species, explainable by standard bond-valence concepts.

Phase separation in glass is a topic of great importance in controlling transparency, crystallization and the microstructure that determines the material's optical and mechanical properties. A technologically relevant borosilicate glass with molar composition 12Na2O-26SiO2-62B2O3 shows dramatic changes of microstructure and mechanical properties upon heat treatment. While heat treatment at 580 °C for 64 h develops a binodal structure with silica-rich dispersions, the glass transforms towards an elongated spinodal-like microstructure when the treatment is extended towards 96 h, producing strong increases in both the elastic modulus and the crack resistance. Solid-state nuclear magnetic resonance (NMR) spectra of the nuclei 29Si, 11B, and 23Na, as well as 23Na{11B} rotational echo double resonance (REDOR) were analyzed in detail and confirm that the short- and medium-range local environments of the constituent nuclei remain completely unaltered during this process. Extended annealing of the samples results in the crystallization of β-sodium octoborate (Na2B8O13) within non-transparent domains, which were characterized in detail by multinuclear NMR spectroscopy. Overall, the NMR work reported in this study supports the conclusion that the remarkable changes in the mechanical properties are purely based on changes in morphology.

The coordination environments of Cu2+ in a copper-doped 2D ZnO-stearic acid (SA) nanocomposite were investigated by Electron Paramagnetic Resonance (EPR) spectroscopy. The material, Zn₀.₉₅Cu₀.₀₅O-(SA)0.13, synthesized following a previously reported procedure, was studied using continuous-wave (CW) EPR at X- and Q-band over the temperature range 30-300 K, together with pulsed EPR at X-band at 15 K. An important part in the analysis of these spectra is the simulation of distributions (strains) of Zeeman- and hyperfine coupling tensor parameters, whose anisotropies are anti-correlated. A significant fraction of the Cu2+ ions is incorporated into the ordered layered structure, where slow thermally activated motions lead to progressive spectral broadening with increasing temperature. These results provide a detailed microscopic picture of the distribution, local symmetry, and dynamics of Cu2+ sites in Zn₀.₉₅Cu₀.₀₅O-(SA)0.13, highlighting the role of structural heterogeneity in shaping their magnetic resonance signatures. Overall, this work develops a general strategy of using paramagnetic probes to investigate structural complexity in similar layered and organic-inorganic materials.

A method to obtain magnetic dipole-dipole coupling information for nuclei exhibiting ultra-wideline NMR spectra in disordered solids is presented. This is achieved via a constant time version of SEDOR (Spin Echo DOuble Resonance) employing WURST (Wideband Uniform Rate Smooth Truncation) pulses and CPMG (Carr Purcell Meiboom Gill) detection. The method - coined CT-WUDOR-CPMG (Constant Time-WURST SEDOR-CPMG) NMR spectroscopy - is tested on Ba2TeO(PO4)2 as a crystalline model compound applying 125Te{31P}-CT-WUDOR-CPMG NMR. Then, 125Te{19F}- and 125Te{31P}-CT-WUDOR-CPMG are performed to obtain structural information on TeO2 - NaPO3 - NaF glasses.

Samples of YPdCd, Y2Pd2Cd and Y2Cu2Cd were synthesized from the elements by induction melting. The three cadmium phases were characterized through their Guinier powder patterns. YPdCd crystallizes with the hexagonal ZrNiAl-type structure (space group P6(-)2m; a = 756.0(4) and c = 384.7(2) pm) The structure of Y2Pd2Cd was refined from single-crystal X-ray diffractometer data: Mo2B2Fe type, tetragonal space group P4/mbm, a = 765.33(3), c = 370.30(2) pm, wR2 = 0.0254, 289 F-2 values and 12 variables. Y2Pd2Cd is a 1:1 intergrowth structure of CsCl and AlB2 related slabs of compositions 'YCd' and 'YPd2'. The palladium dumb-bells (279 pm Pd-Pd) and the cadmium atoms (301 pm Cd-Pd) form a two-dimensional [Pd2Cd] substructure that is separated by yttrium layers in c direction. Consistent with their crystal structures, the Cd-113 solid-state MAS-NMR spectra of Y2Pd2Cd and isotypic Y2Cu2Cd show only one signal characterized by strong Knight shift contributions.

The structure of the metasilicate composition glasses (A2O)x(XO)0.50−x(SiO2)0.50, with A = Na or K, X = Mg, Zn, or Ca, and x = 0.25 or 0.33, was investigated by combining neutron and high-energy x-ray diffraction with Raman scattering and 29Si and 25Mg magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The latter employed the rotor-assisted population transfer approach for signal enhancement. The diffraction results show a substantial population of four-coordinated X2+ cations in the majority of the magnesium- and zinc-bearing glasses. Based on the average degree of polymerization of the silicate networks obtained from the solid-state 29Si NMR results, and supported by the findings from Raman spectroscopy, no compelling evidence could be found for a network-forming role for the four-coordinated Mg2+ and Zn2+ species. The relationship between the Mg–O coordination numbers measured by diffraction and the mean isotropic chemical shifts found from 25Mg MAS NMR spectroscopy is considered for a variety of silicate glasses. A clear correlation between these parameters could not be found.

The structure of (Nb2O5)x(NaPO3)1-x glasses was re-visited by combining neutron and high energy x-ray diffraction with Raman scattering over a wide composition range. The results were interpreted by reference to the phosphorus atom speciation found from a novel analysis of 31P magic angle spinning nuclear magnetic resonance spectra [Ensuncho et al., J. Am. Chem. Soc. 147, 31147 (2025)]. The results indicate a distorted octahedral coordination environment for the Nb atoms across the composition range. The measured x-dependence of (i) the mean numbers of non-bridging oxygen (NBO) atoms and P-O-P and P-O-Nb connections per phosphate group, and (ii) the fraction of oxygen atoms in Nb-O-Nb connections, are described by a self-consistent analytical model in which there is a preferential formation of heteronuclear P-O-Nb bonds within a network structure formed by 4- and 6-coordinated P and Nb atoms, respectively, such that P-O-P connections are absent when the niobia content exceeds x ∼ 0.22. At smaller x, the non-bridging oxygen atoms are distributed among the P- and Nb-centered polyhedral units. The model provides a connectivity density that accounts for the rapid increase in the glass transition temperature with increasing Nb2O5 content and shows that the enhancement to the non-linear optical properties for x > 0.2 is related to a more rapid increase with x in the fraction of oxygen atoms involved in polarizable Nb-O-Nb connections. The methodology also suggests that the dissolution rate measured for the (Nb2O5)x(Na2O)0.4(P2O5)0.6-x glass series is dependent on the proportion of P-O-P linkages.

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.

The stannide Li4Rh3Sn5 was synthesized by induction-melting of the elements in a sealed tantalum ampoule. The sample was characterized by powder X-ray diffraction and the Li4Rh3Sn5 structure was refined from single-crystal X-ray diffractometer data: new type, orthorhombic space group Pnnm, a = 813.27(11), b = 2,259.6(3), c = 449.94(6) pm, wR2 = 0.0486, 1577 F-2 values and 64 variables. The rhodium and tin atoms form a rigid covalently bonded three-dimensional [Rh3Sn5] network with Rh-Sn distances ranging from 263 to 277 pm. Within this network, the tin atoms form two different substructures, i. e., angled Sn1-Sn4-Sn5 units and isolated Sn2 and Sn3 atoms. The lithium atoms fill cages within the [Rh3Sn5] network. They have coordination numbers 11, 12 and 13. Based on their different Li-7 resonance shifts two groups of distinct local environments can be identified in an intensity ratio of 3:1, namely the 4g Wyckoff sites Li1, Li2, and Li5, and the 2c Wyckoff sites Li3 and Li4. The whole Li4Rh3Sn5 structure can be described by condensation of the Li1@LiRh4Sn6, Li2@Li2Rh4Sn6, Li3@Li2Rh4Sn6, and Li4@Li2Rh4Sn6 polyhedra, including the Li5 atoms which are within the Li1 coordination sphere. The Sn-119 M & ouml;ssbauer spectrum of Li4Rh3Sn5 shows a superposition of two sub-signals in a ratio of 60:40. The two sub-signals with similar isomer shift are discernable through their quadrupole splitting parameters: similar to 1.93 mm s(-1) for the tin atoms of the angled Sn-3 unit, and similar to 1.20 mm s(-1) for the isolated tin atoms with a more symmetric electron density distribution.

Oxygen-deficient perovskites exhibit promising ionic conductivity for electrochemical applications, but understanding their structure-property relationships requires detailed knowledge of local atomic environments. In this study, we employ multinuclear (17O, 45Sc, and 71Ga) solid-state NMR spectroscopy to investigate the local structure of cubic Sr2ScGaO5 (c-SSGO). 17O NMR signals were assigned based on 17O{45Sc} transfer of population double resonance experiments (TRAPDOR) and ab initio chemical shift calculations using the CASTEP code. Our results provide compelling evidence that despite its cubic average structure determined by X-ray Bragg diffraction, the local atomic arrangement in c-SSGO closely resembles the orthorhombic brownmillerite structure, as previously proposed from neutron diffraction pair distribution (PDF) analysis. Furthermore, we demonstrate how solid-state NMR, together with DFT calculations of 17O NMR chemical shifts can serve to discriminate between alternative structural scenarios for defect perovskite structures. The study highlights the power of solid-state NMR in elucidating local structural details in complex oxides with local variations in their crystal structures.

Multicomponent glasses containing a diverse range of element oxides are increasingly being designed using machine learning (ML) techniques to optimize their properties. These rather complex compositions present new opportunities for both fundamental research and materials development. A key challenge in ML-assisted and empirical glass design is establishing quantitative structure-property relationships (QSPRs), which serve as critical input parameters for predictive modeling. In this study, we systematically examine the contrasting structural roles of niobium oxide (Nb2O5) and lanthanum oxide (La2O3) in multicomponent silicate glasses using multinuclear solid-state NMR and Raman spectroscopy. The glass compositions, in mol%, are approximately xLa2O3-(100-x)[28(Li2O-Na2O-K2O)-12(CaO-SrO-BaO)-60SiO2] and xNb2O5-(100-x)[28(Li2O-Na2O-K2O)-12 (CaO-SrO-BaO)-60SiO2], with 0 <= x <= 10. Our results demonstrate that Nb2O5 primarily acts as a network former, integrating into the silicate framework and forming Si-O-Nb linkages, without the formation of additional non-bridging oxygen (NBO) atoms in the silicate network. The 93Nb NMR chemical shifts indicate that six-coordinate [NbO6/2]- units are formed, which are charge compensated by alkali or alkaline-earth oxides. In contrast, La2O3 functions as a network modifier, introducing approximately 3.4 NBOs per equivalent of La2O3 and decreasing the connectivity of the silicate network accordingly. While 93Nb and 139La NMR spectra suggest a relative invariance in Nb and La local environments as a function of composition, additional 7Li{93Nb} double resonance NMR experiments give evidence for non-linear changes of the Li/Nb interaction strengths. The 7Li and 23Na chemical shift trends reveal distinct interactions between Li+/Na+ and the modified glass network. These findings highlight key structural differences between Nb2O5-and La2O3-containing silicate glasses, contributing to the development of data-driven glass design strategies.

Der Festkörperchemiker Robert Schöllhorn war ein anspruchs‐ und hingebungsvoller Lehrer und Forscher, der maßgeblich zum Verständnis von Redox‐Konzepten und der Reaktivität von Interkalationsverbindungen beigetragen hat.

The structural role of Nb2O5 in oxide glasses remains poorly understood, despite the unique linear and nonlinear optical properties that it bestows. Here, advanced solid-state NMR methods can yield valuable insight, but their full potential has been underutilized for niobium-containing systems, especially in respect of the dipolar techniques that provide quantitative information on the interatomic connectivity and distance distributions. This study presents a new NMR-strategy and applies it to the model glass system xNb2O5-(100-x)NaPO3 (0 ≤ x ≤ 40). The number of P-O-P linkages per P atom is estimated from the 31P-31P dipole-dipole interactions using spin echo decay (SED) and double-quantum based dipolar recoupling effecting nuclear alignment reduction (DQ-DRENAR). The number of P-O-Nb linkages is obtained from the 31P-93Nb dipolar coupling using 93Nb{31P} rotational echo double resonance (REDOR) and, for the first time, 31P{93Nb} rotational echo saturation pulse double resonance (RESPDOR). Constrained by these interaction-selective experiments, which also include 31P/23Na double resonance spectroscopy, the poorly resolved 31P MAS NMR spectra are quantitatively decomposed into their contributions from the various network-forming units. Additional field dependent 93Nb MAS NMR experiments provide chemical shift parameters that reveal multiple six-coordinate niobium environments with varying degrees of distortion. Overall, the results demonstrate that Nb2O5 assumes a network former role, increasing the overall network connectivity. They also demonstrate an advanced solid-state NMR protocol for characterizing the structural role of Nb2O5, an important intermediate oxide, in multicomponent glasses.

Samples of YPdCd, Y 2 Pd 2 Cd and Y 2 Cu 2 Cd were synthesized from the elements by induction melting. The three cadmium phases were characterized through their Guinier powder patterns. YPdCd crystallizes with the hexagonal ZrNiAl-type structure (space group P 6 ‾ $\overline{6}$ 2 m ; a = 756.0(4) and c = 384.7(2) pm). The structure of Y 2 Pd 2 Cd was refined from single-crystal X-ray diffractometer data: Mo 2 B 2 Fe type, tetragonal space group P 4/ mbm , a = 765.33(3), c = 370.30(2) pm, w R 2 = 0.0254, 289 F 2 values and 12 variables. Y 2 Pd 2 Cd is a 1:1 intergrowth structure of CsCl and AlB 2 related slabs of compositions ‘YCd’ and ‘YPd 2 ’. The palladium dumb-bells (279 pm Pd–Pd) and the cadmium atoms (301 pm Cd–Pd) form a two-dimensional [Pd 2 Cd] substructure that is separated by yttrium layers in c direction. Consistent with their crystal structures, the 113 Cd solid-state MAS-NMR spectra of Y 2 Pd 2 Cd and isotypic Y 2 Cu 2 Cd show only one signal characterized by strong Knight shift contributions.