Oxynitride Glasses Research Articles

Effect of composition on the thermal properties and structure of M-Al-Si-O-N glasses, M = Na, Mg, Ca

The primary objective of this study is to explore the relationship between the composition, structure, and thermal characteristics of M-Al-Si-O-N glasses, with M representing sodium (Na), magnesium (Mg), or calcium (Ca). The glasses were prepared by melting in a quartz crucible at 1650 °C and AlN precursor (powder) was utilized as a nitrogen source. The measured thermal properties studied were glass transition temperature (Tg), crystallization temperature (Tc), glass stability, viscosity, and thermal expansion coefficient (α). The findings indicate that increasing the aluminum content leads to higher glass transition, crystallization temperatures, and viscosities. In contrast, fragility values increase with the Al contents, while modifier elements and silicon content influence thermal expansion coefficient values. FTIR analysis revealed that in all glasses, the dominant IR bands are attributed to the presence of Q2 and Q3 silicate units. The effect of Al is observed as a progressive polymerization of the silicate network resulting from the glass-forming role of Al2O3. In most samples, the Q4 silicate mode was also observed, strongly related to the high Al content. Overall, the study shows that the complexity of composition-property correlations where the structural changes affect the properties of Mg/Ca-based oxynitride glasses has potential implications for their use in various technological fields.

Li concentration change around Cu/LiPON interface measured by TOF-ERDA

Lithium metal is a promising anode material for the development of advanced all-solid-state batteries (ASSBs) with high energy density. Among the various solid electrolytes, lithium phosphorus oxynitride glass electrolyte (LiPON) is notable for facilitating stable Li plating-stripping reactions in ASSBs employing Li metal. The aim of this study is to examine the Li/LiPON interface, with a specific emphasis on the reductive decomposition of LiPON near this interface. We employed time-of-flight elastic recoil detection analysis (TOF-ERDA) to assess changes in Li concentration around the Cu/LiPON interface immediately prior to the Li plating reaction. Our electrochemical measurements indicate that critical decomposition of LiPON occurs when the voltage at the Cu electrode is reduced to 0.1 V vs. Li/Li+ at 25 °C, resulting in the in situ formation of Li3P operating at 0.7 V vs. Li/Li+ as an anode material. The TOF-ERDA findings reveal that this decomposition reaction results in a layer with partial decomposition (ranging from 5 to 25% on average) extending up to approximately 30 nm from the Cu/LiPON interface. This insight is vital for enhancing the design and performance of ASSBs.Graphical abstract

LiPON/Multilayer-Graphene Interface Enables High-Rate Charging and Discharging

Graphite is the anode-active material commonly used in LIBs. In LIB, solid electrolyte interphase (SEI) is formed by the reduction of the liquid electrolyte, and the SEI plays a role as a passive film. In the charging process, Li ions transport in the liquid electrolyte and SEI, desolvation reactions of Li ions occur, and then Li ions insert into the graphite anode. It has been reported that the desolvation reaction of Li ions is the rate-limiting process[1]. Lithium phosphorous oxynitride glass (LiPON) is a well-known material as a solid electrolyte. However, it has been reported that the electrochemical window of LiPON ranges from 0.68 V to 2.63 V[2]. Therefore, it is possible that the decomposition reaction of LiPON occurs when the electrochemical cell is charged. Since the decomposition products can be a resistance, LiPON that is not easily reduced is required. In this study, we focused on the lithium phosphorus oxynitride glass (LiPON) electrolyte/multilayered graphene (MGr) film interface as an example without the desolvation process. In addition, we have investigated the relationship between LiPON composition ratio, electronic properties, and interfacial resistance by changing the sputtering conditions for LiPON film. Consequently, we found that the charge-transfer resistance at the MGr/LiPON interface was significantly small, although the MGr/LiPON interface was supposed to have inorganic solid electrolyte interphase resulting from the LiPON reduction decomposition. The figure shows a schematic illustration of the Liquid Electrolyte/MGr interface and the LiPON/MGr interface. Figure 1

Elucidating photoluminescent properties of Eu‐doped Ca–Al–Si–O(–N) glasses and the local structures of Eu ions

AbstractEuropium (Eu) ion–doped luminescent materials have attracted considerable attention for their numerous optical applications. Eu‐doped Ca–Al–Si–O(–N) glasses were synthesized from a mixture of oxynitride glasses and Eu2O3 powder using a standard melt‐quenching technique in a radiofrequency furnace. The source Eu trivalent ions primarily changed to Eu2+ during melting, and the ratio of Eu2+ ions increased with an increase in Eu content in the starting mixture. All the prepared glasses exhibited photoluminescence (PL) owing to the 5d–4f transition of Eu2+ ions. The absorption edge and PL wavelength shifted to longer wavelength with an increase in Eu content. Moreover, oxynitride glasses exhibited a longer wavelength than those of oxide glasses. The internal quantum efficiency (IQE) increased with the increase in Eu content until it reached a maximum. X‐ray absorption structure and electron spin resonance spectroscopies were used to determine the local structure of Eu ions, which confirmed that changes in the local structure of Eu ions were responsible for the shift in PL peak and the change in IQE. The development of the Eu‐doped Ca–Al–Si–O–N glasses is highly inspiring for transparent phosphors.

Electrochemical Li+ Insertion/Extraction Reactions at LiPON/Epitaxial Graphene Interfaces.

Redox reactions of the Li+ insertion/extraction from one to two interlayers of graphene (Gr) on area-defined single-crystalline SiC substrates are investigated using lithium phosphorus oxynitride glass (LiPON) as the solid-state electrolyte. Unlike an organic liquid electrolyte, this glassy electrolyte does not induce a reduction current and excludes the desolvation reaction of Li+. Gr electrodes with less than two Gr layers show a single reduction peak and one or two oxidation peaks below +0.21 V (vs Li+/Li), differing distinctly from those of graphite and multilayer Gr, which display multiple peaks (multiple stage transitions). However, this finding aligns with the conventional understanding that graphite stage structure transitions proceed with stepwise increases or decreases in the number of Gr layers between adjacent Li-inserted interlayers. Cyclic voltammetry measurements indicate the presence of surface capacity due to Li+ adsorption/desorption at the LiPON/Gr interface. Moreover, Li+ insertion and extraction induce different charge transfer resistances at the level of a single interlayer. These sensitive measurements are achieved using high-quality epitaxial Gr and LiPON electrolyte, which prevent the formation of a solid electrolyte interphase and the desolvation reaction of Li+. Similar measurements using bilayer Gr produced by chemical vapor deposition coupled with a Gr transfer method and an ethylene carbonate/dimethyl carbonate liquid electrolyte are not reliable. Thus, the proposed method is effective for electrochemical measurement of Gr electrodes with a controlled number of layers.

Hertzian crack propagation in graded glass/ceramic composites

AbstractIn literature, the concept of material gradation is shown to inhibit surface crack initiation in glass/ceramic composites subjected to Hertzian indentation. However, surface cracks could yet initiate due to relatively higher loadings or in the presence of surface flaws/defects. Hence, characterization of graded composites concerning the resistance against Hertzian crack initiation and propagation manifests itself as a prominent matter. In this study, axisymmetric Hertzian cracks evolving in graded glass/ceramic composites propelled by a rigid cylindrical punch are investigated employing a novel recursive method, called the stacked‐node propagation procedure. Crack trajectories and their propagation susceptibilities are predicted via the minimum strain energy density (MSED) criterion regarding the crack growth resistance (R‐curve) of ceramics. The stress trajectory approach is also considered for a homogeneous glass to reveal the reliance and effectiveness of the MSED criterion in the present crack problems. The Mori–Tanaka relations are adopted to model the elastic modulus and Poisson's ratio variations through the composites, which are implemented on the simulations via the homogeneous finite element approach. Hertzian crack problem of a practically producible graded composite comprised of oxynitride glass and a fine‐grained silicon nitride ceramics (Si3N4) is treated as a case study. The degree of material gradation is assessed for the mitigation of surface crack initiation and propagation risks.

Composition–structure–property relationships of transparent Ca–Al–Si–O–N oxynitride glasses: The roles of nitrogen and aluminum

AbstractWe explore the formation and composition–structure–property correlations of transparent Ca–Al–Si–O–N glasses, which were prepared by a standard melt‐quenching technique using AlN as the nitrogen source and incorporating up to 8 at.% of N. Their measured physical properties of density, molar volume, compactness, refractive index, and hardness—along with the Young, shear, and bulk elastic moduli—depended roughly linearly on the N content. These effects are attributed primarily to the improved glass‐network cross‐linking from N compared to O, rather than the formation of higher‐coordination AlO5and AlO6groups, where27Al magic‐angle‐spinning nuclear magnetic resonance experimentation revealed that aluminum is predominately present in tetrahedral coordination as AlO4units. Yet, several physical properties, such as the refractive index along with the bulk, shear, and Young's elastic moduli, increase concomitantly with the Al content of the glass. We discuss the incompletely understood mechanical–property boosting role of Al as observed both herein and in previous reports on oxynitride glasses, moreover suggesting glass‐composition domains that are likely to offer optimal mechanical properties.

Review: Elaboration, structure, and mechanical properties of oxynitride glasses

AbstractOxynitride glasses are glasses where threefold coordinated nitrogen atoms substitute for twofold oxygen ones, hence resulting in a larger interatomic cross‐linking degree. Such glasses were first observed at the grain boundary in silicon nitride ceramics, where they govern the high‐temperature behavior. Later, they were prepared as bulk materials and motivated numerous researches, thanks to their large viscosity, glass transition range, elastic moduli, hardness, and fracture toughness among inorganic and non‐metallic glasses. In different chemical systems that were investigated, the synthesis routes and the sources for these exceptional mechanical properties are reviewed. Oxynitride glasses are not easy to process and suffer from the loss of transparency as nitrogen is incorporated over some critical content. Nevertheless, they are attractive “specialty” glasses in various niche areas, thanks to their large refractive index and dielectric constant, improved chemical durability, high softening point, etc., and majorly to their exceptional mechanical properties.

Mechanical properties of oxynitride glasses

AbstractOxynitride glasses combine a high refractoriness, with Tg typically >850°C, and remarkable mechanical properties in comparison with their parent oxide glasses. Their Young's modulus and fracture toughness reach 170 GPa and 1.4 MPa m.5, respectively. Most reports show good linear relationships between glass property values and nitrogen content. There is a clear linear dependence of Young's modulus and microhardness on fractional glass compactness (atomic packing density). They also have a better resistance to surface damage induced by indentation or scratch loading. The improvements stem from the increase of the atomic network cross‐linking—because of three‐fold coordinated nitrogen—and of the atomic packing density, despite nitrogen being lighter than oxygen and the Si–N bond being weaker than the Si–O bond. For constant cation composition, viscosity increases by ∼3 orders of magnitude as ∼17 eq.% oxygen is replaced by nitrogen. For rare earth oxynitride glasses with constant N content, viscosity, Young's modulus, Tg, and other properties increase with increasing cation field strength (decreasing ionic radius). Research continues to find lighter, stiffer materials, including glasses, with superior mechanical properties. With higher elastic moduli, hardness, fracture toughness, strength, surface damage resistance, increased high temperature properties, oxynitride glasses offer advantages over their oxide counterparts.

Investigation of local structures of silicon oxynitride glasses prepared from aerogels

Investigation of local structures of silicon oxynitride glasses prepared from aerogels

Elastic Properties and Hardness of Mixed Alkaline Earth Silicate Oxynitride Glasses.

The incorporation of nitrogen as a second anion species into oxide glasses offers unique opportunities for modifying glass properties via changes in glass polymerization and structure. In this work, the compositional dependence of elastic properties and the nanoindentation hardness of mixed alkaline-earth silicate oxynitride glasses containing a high amount of nitrogen (>15 at.%, c.a. 35 e/o) were investigated. Three series of silicon oxynitride glass compositions AE–Ca–Si–O–N glasses (where AE = Mg, Sr, and Ba) having varying amounts of modifiers were prepared using a new glass synthesis route, in which a precursor powder of metal hydrides was used. The obtained glasses contained high amounts of N (19 at.%, c.a. 43 e/o) and modifier cations (26 at.%, c.a. 39 e/o). Mg–Ca–Si–O–N glasses had high values of nanohardness (12–16 GPa), along with a reduced elastic modulus (130–153 GPa) and Young’s modulus (127–146 GPa), in comparison with the Sr–Ca- and Ba–Ca-bearing oxynitride glasses. Both the elastic modulus and the nanohardness of AE–Ca–Si–O–N glasses decreased with an increase in the atomic number of the AE element. These property changes followed a linear dependence on the effective cation field strength (ECFS) of the alkaline earth (AE) modifier, according to their valences and ionic radii. No mixed alkaline-earth effect was observed in the current investigation, indicating that the properties were more dictated by the nitrogen content.

Lithium-ion conductivity and crystallization temperature of multicomponent oxide glass electrolytes

Lithium-ion-conducting oxide glass electrolytes in the multicomponent systems Li 2 O–B 2 O 3 –SiO 2 –P 2 O 5 -LiX (LiX = Li 3 N, Li 2 SO 4 , Li 2 CO 3 , and LiI) were synthesized using a mechanochemical technique. The crystallization temperature and ionic conductivity of multicomponent glasses with added lithium salts or Li 3 N were evaluated. Because the crystallization temperature is a measure of the ability of glasses to resist crystallization at high temperature, glasses with high conductivity and high crystallization temperature are desirable electrolytes. In this study, the lithium-ion conductivity of the glasses was found to be correlated with the crystallization temperature, and it was difficult to increase both the conductivity and crystallization temperature. The addition of lithium salts (Li 2 SO 4 , Li 2 CO 3 , and LiI) increased the conductivity but decreased the crystallization temperature. Nitrogen doping by the addition of Li 3 N improved both these properties of the oxide glass electrolyte. Therefore, oxynitride glasses are desirable electrolytes owing to their thermal stability and lithium-ion conductivity. • Li 2 O-based multicomponent oxide glasses are prepared via mechanochemistry. • Lithium ion conductivity of glasses is correlated with crystallization temperature. • The addition of lithium salts increases conductivity but decreases thermal stability. • Nitrogen-doping to oxide glasses improves both those properties.

In Vitro Dissolution of Na-Ca-P-Oxynitrides.

Sodium-calcium-phosphate based oxynitride glasses and glass-ceramics doped with Mg, Si, and Nb were studied in vitro in simulated body fluid (SBF) under static conditions. The release of ions and pH changes up to 7 days of immersion were investigated. The nitrogen incorporation into phosphate glass matrix was found to notably influence in vitro dissolution only of homogenous glasses. Increasing the nitrogen content in the samples decreased the mean mass loss, while the niobate incorporation increased it. The correlation between the nitrogen content and increase in pH of SBF was also observed. The presence of phosphates crystallites was found to support the dissolution process at the beginning step (up to 3 days).

Corrigendum to “Synthesis of bulk silicon oxynitride glass through nitridation of SiO2 aerogels and determination of Tg”

The manuscript titled “Synthesis of bulk silicon oxynitride glass through nitridation of SiO2 aerogels and determination of Tg” was published with error in order of author affiliations, please find the correct order above. This Corrigendum acknowledges and corrects the error.

Investigation of luminescence properties of Eu-doped Si-Al-O-N glasses synthesized via sol-gel process

Luminescent properties of Eu ions doped in Si-Al oxynitride glasses were investigated. The Si-Al oxynitride glasses contained with Eu ions were prepared via sol-gel processes and nitridation. The nitrogen in the glasses prepared from xerogels was less than 3 at%, but that in the glasses prepared from aerogels increased up to approximately 20 at% with an increase in the nitridation temperature. The glass structures were characterized using FTIR and NMR spectroscopy. The valence states of Eu ions were estimated by XANES spectroscopy. All samples showed a broad emission peak originating from 4f→5d transition of Eu2+ ions. The luminescent properties such as photoluminescence intensity and the peak position depended on the glass compositions. The effects of the glass compositions on the luminescent properties were investigated based on the glass structures.

Topological hardening through oxygen triclusters in calcium aluminosilicate glasses

AbstractMolecular dynamics simulations and topological constraint theory are used to study the impact of oxygen triclusters in the calcium aluminosilicate glass system at ratios of 0.6, 1, 1.5, 2, and 4 [Al2O3]/[CaO]. Negligible percentages (less than ~3%) of five‐coordinated Al structures are found at all ratios. Up to ~27% three‐coordinated oxygens, also known as triclusters, are found at the highest ratio of [Al2O3]/[CaO]. A topological constraint model, which considers additional constraints provided by triclusters, is created to predict the glass transition temperature, hardness, and Young's modulus. The models are used to elucidate the role of triclusters in glass properties. Analysis of topological constraints shows that triclusters can potentially increase the glass hardness within the calcium aluminosilicate system. The results are also compared to oxynitride glasses. Triclusters show the same ability as nitrogen to increase the glass hardness but are less effective at increasing the Young's modulus.

Microstructure Evaluation and Impurities in La Containing Silicon Oxynitrides.

Oxynitride glasses are not yet commercialised primarily due to the impurities present in the network of these glasses. In this work, we investigated the microstructure and instinctive defects in nitrogen rich La−Si−O−N glasses. Glasses were prepared by heating a powder mixture of pure La metal, Si3N4, and SiO2 in a nitrogen atmosphere at 1650–1800 °C. The microstructure and impurities in the glasses were examined by optical microscopy, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy in conjunction with electron energy-loss spectroscopy. Analyses showed that the glasses contain a small amount of spherical metal silicide particles, mostly amorphous or poorly crystalline, and having sizes typically ranging from 1 µm and less. The amount of silicide was estimated to be less than 2 vol. %. There was no systematic relation between silicide formation and glass composition or preparation temperature. The microstructure examination revealed that the opacity of these nitrogen rich glasses is due to the elemental Si arise from the decomposition reaction of silicon nitride and silicon oxide, at a high temperature above ~1600 °C and from the metallic silicide particles formed by the reduction of silicon oxide and silicon nitride at an early stage of reaction to form a silicide intermetallic with the La metal.

Synthesis of bulk silicon oxynitride glass through nitridation of SiO2 aerogels and determination of Tg

AbstractThe development of transparent glass for use in high‐temperature applications is continuing. In this study, we synthesized bulk silicon oxynitride glasses (a‐Si(O,N)x) through the nitridation of SiO2 aerogels containing methyl (CH3‐) groups and evaluated their bulk properties, including their glass transition temperature (Tg). Tetramethyl orthosilicate and methyltrimethoxysilane were added into the precursor gels, and those gels were subjected to a supercritical CO2 drying process. The presence of CH3‐group in the gel avoided cracking during ammonolysis at 750°C–1400°C, and the transparency of the gel was remained even after ammonolysis at 1300°C. The ammonolysis successfully introduced nitrogen into the gels even at relatively low temperatures, for example, 750°C, and the highest nitrogen content (11.7 mass%) was achieved in the gel after ammonolysis at 1300°C. As the nitrogen‐related signals in electron spectroscopy indicated presence of nitride ions (N3−) after ammonolysis and the infrared absorption signals attributed to Si–N bonds were enhanced with the increase of nitrogen concentration, we successfully obtained oxynitride glasses. Those oxynitride glasses showed increase of Tg with their nitrogen concentration.

Effect of nitrogen on the antibacterial behavior of oxynitride glasses

The main drawback of bioglasses is their restricted use in load bearing applications and the consequent need to develop stronger glassy materials. This has led to the consideration of oxynitride glasses for numerous biomedical applications. This paper investigated two different types of glasses at a constant cationic ratio, with and without nitrogen (a N containing and a N-free glass composition) to better understand the effect of N on the biological properties of glasses. The results revealed that the addition of N increased the glass transition temperature, isoelectric point (IEP) and slightly increased wettability. Moreover, compared to N including glass, N-free glass exhibited better anti-bacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), two key bacteria that infect implants. In summary, these in vitro results indicated that amine functional groups existing in N containing glasses which are missing in N-free glasses, caused a slight difference in wetting behavior and a more obvious change in isoelectric point and in bacterial response. N-free glasses exhibited better inhibitory results both against E. coli and S. aureus compared to N including glass suggesting that oxygen rich glasses should be further studied for their novel antibacterial properties.

Antibacterial behavior of oxynitride glasses as a glassy grain boundary phase for silicon nitride‐based ceramics

AbstractSilicon nitride‐based ceramics have provided significant advantages due to their high chemical resistance, high elastic modulus, and combination of hardness and fracture toughness (depending on self‐reinforcement). Over the past two decades, a significant amount of interest has been generated for the bio‐applications of these materials. However, the effect of the grain boundary phase on such applications is still not very well understood. In this study, the effect of different cations on biological (such as antibacterial and cytocompatibilty) and material properties (like wetting angles and isoelectric points [IEP]) of oxynitride glasses, mimicking the grain boundary phase in Si3N4 and SiAlON ceramics, were investigated. Results revealed that the antibacterial behavior and mammalian cell viability were inversely correlated in glasses with rare‐earth cation additions. Ca was the best cation when the two properties (bacterial response and cell proliferation) were considered together, and, thus should be further studied for a wide range of applications.