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Constructing type II heterostructures represents a widely recognized strategy for enhancing charge separation and photocatalytic efficiency, but it remains challenging to fabricate homologous heterostructures based on visible-light-responsive semiconductors, especially for popularly investigated (oxy)nitrides with low thermal stability. Here, we synthesized a homologous heterostructure (denoted as YTON_H) based on the oxynitrides of YTaO4−xNy and YTaON2. This heterostructure exhibits type II band structure alignment and intimate interface achieved through a magnesium (Mg) powder-assisted nitridation method. Compared with widely reported heterologous heterostructures, the as-obtained YTON_H homologous heterostructure could similarly exhibit enhanced charge separation as well as photocatalytic water splitting performance with respect to its counterparts (YTaO4−xNy and YTaON2). Meanwhile, detailed structural characterizations and spectroscopy analysis have been made to confirm the formation of heterostructure and promotion of spatial charge separation. [ABSTRACT FROM AUTHOR]

In contrast to a steam pressure regulator, a nitrogen pressurizer offers several advantages, including enhanced maneuverability, a straightforward design, and a compact size. Within nuclear reactors utilizing nitrogen pressurization, nitrogen gas in the reactor core area undergoes decomposition under radiation and interacts with radiation-induced byproducts of water, resulting in the formation of nitrogen hydrides and nitrogen oxides, which impacts the management of water quality within the primary cooling circuit and may leading corrosion intensification. The present numerical model of nitrogen decomposition product yields in the primary circuit is predominantly dependent on a computational model rooted in the kinetics of reactions. This approach involves tackling an extensive set of non-linear equations, which, in turn, hinges on unknown experimental factors. As a result, the current methodology leans heavily on a multitude of conjectures, and the condition number of its Jacobi matrix is notably high, giving rise to substantial calculation inaccuracies, spanning from −50% to 100%. Therefore, this paper aims to establish an accurate and well-convergent numerical computational model to guide the water chemistry control of nitrogen-pressurized reactor systems. From a thermodynamic perspective, the paper employed the radiation chemical yield (g-value) and equilibrium constant method to construct a decomposition calculation model for water dissolving nitrogen in a radiation filed. Specifically, the work employed point-by-point steady state hypothesis, considering that the chemical state reaches equilibrium at each time point. The model solved ten chemical equilibrium equations, an atom conservation equation and an electronic conservation equation at each time point, and simulated the time effect of radiation by changing the primary conditions at each step. Within the temperature range of 288 K to 473 K, this model exhibited relative errors from reported experimental data ranging from −60% to 10%. Employing this model, calculations to ascertain changes in coolant ion concentrations were conducted under reactor operating conditions. Furthermore, the paper presents an in-depth analysis of how calculation parameters influence the obtained results. The research reveals a consistent trend in the pH value, showing a gradual decrease under irradiation until it reaches a slightly acidic state, which comes from a relatively high concentration of NO ions, emphasizing the need for the addition of alkalizing agents during practical reactor operation to maintain suitable water quality. Additionally, the paper delves into an analysis of how different reactor parameters affect the equilibrium state. Notably, a linear relationship is identified between temperature/nitrogen concentration and the concentrations of typical ions. In contrast, the radiation dose rate does not exert a substantial influence on the final outcomes. This work carries significant reference value for the design of nitrogen pressurized reactors.

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The structural properties of NbON oxynitride under high pressure were investigated through in situ synchrotron X-ray diffraction (SXRD) up to 43 GPa. It was found that the bulk modulus of baddeleyite NbON (290 GPa) is larger than that of ZrO2 (150 GPa), indicating that the introduction of highly covalent nitrogen imparts greater stiffness. Furthermore, SXRD patterns reveal the emergence of a peak signaling a new crystalline phase above around 20 GPa. This is in contrast to TaON, where diffraction patterns only show an increase in background beyond 33 GPa. First-principle calculations suggest that the high-pressure phase adopts an orthorhombic cotunnite-type structure, distinguishing it from the oxide counterparts, wherein the ambient pressure phase transforms to a cotunnite structure via an orthorhombic-I structure. [ABSTRACT FROM AUTHOR]

Using Eu2O3, BaCO3, Si3N4 and SiO2 as starting materials, we succeeded in synthesizing BaSi4O6N2:Eu 2 + by firing the mixture at 1100∘C for 2 h in a reducing atmosphere (N2(95%)–H2(5%)). As a result, a single phase was obtained by setting the charge composition ratio to Si/ Ba = 6. When the Eu 2 + activation amount was 1%, it showed a broad emission in the range of 400–600 nm under the excitation light of ultraviolet rays at 320 nm. This phosphor exhibited chromaticity coordinates of (x , y) = (0. 2 5 8 , 0. 2 9 7) under irradiation with ultraviolet rays at 320 nm and is thought to be a promising phosphor for ultraviolet-excited white LEDs. [ABSTRACT FROM AUTHOR]

Europium (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. [ABSTRACT FROM AUTHOR]

Synthesis of N-doped MgTiO3 with an ilmenite structure was examined as a new ilmenite-type oxynitride material. N-doped MgTiO3 with Scsubstitution was successfully obtained by flux-assisted nitridation using a LiCl-KCl eutectic under pure NH3 or 5% NH3. The oxynitrides gave visible light absorption which MgTiO3 did not show, and were active for sacrificial O2 evolution using AgNO3 under visible light irradiation. [ABSTRACT FROM AUTHOR]

In the present work, a novel n‐UV convertible colour‐tunable emitting phosphor was obtained based on the efficient Ce3+‐Tb3+ energy transfer in the Y10Al2Si3O18N4 host. By properly controlling the ratio of Ce3+/Tb3+, the colour hue of the obtained powder covered the blue and green regions, under excitation of 365 nm. The steady‐state and dynamic‐state luminescence measurement was performed to shed light on the related mechanism, which was justified by the electronic dipole–quadrupole dominating the related energy transfer process. Preliminary studies showed that Y10Al2Si3O18N4:Ce3+,Tb3+ can be promising as an inorganic phosphor for white LED applications. [ABSTRACT FROM AUTHOR]

Selective emission of green light phosphor powder Y4SiAlO8N as the host material and Tb3+ as the activator was successfully achieved using spray pyrolysis (SP). Samples synthesized with various calcination temperatures and precursor concentrations indicated that the most suitable parameter for the synthesized powder is the calcination of 0.05 M Y3.92SiAlO8N:0.08Tb3+ at a temperature of 1600 °C. The effect of the selected parameters was substantiated by the high purity of the Y3.92SiAlO8N:0.08Tb3+ phase, as confirmed by X-ray diffraction (XRD) analysis. The Scherrer equation was used to calculate grain size. In addition, scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDS) confirmed the presence of micron-sized particles, which matched well with the theoretical chemical composition. The specific surface area of the phosphor powder was determined using the Brunauer–Emmett–Teller method. Finally, fluorescence spectrometry was used to determine the luminescence properties. The correlation between the crystallinity of the phosphor powder and narrowing emission is also discussed.

Barium oxide is a conventional promoter for various transition‐metal (TM) catalysts in ammonia synthesis. Ba‐promoted Ru catalysts are widely used for ammonia synthesis under mild reaction conditions. However, the promotion mechanism, including the active factor, remains unclear. In this study, the excellent promotion effect of barium oxynitride is reported, which creates anionic electrons in the lattice, forming an electride (BaOxNy:e−z) with the same rocksalt structure as BaO. The BaOxNy:e−z enhances the ammonia synthesis activity of the supported Ru catalyst by 40–100 fold compared with the BaO promotor. This study reveals that a low‐work‐function electron formed in the BaO lattice plays a pivotal role in the electronic promotion effect in catalytic ammonia synthesis, suggesting that BaOxNy:e−z formed near the surface during the ammonia synthesis reaction is an active species for the promotion effect of conventional BaO. [ABSTRACT FROM AUTHOR]

Selective emission of green light phosphor powder Y4SiAlO8N as the host material and Tb3+ as the activator was successfully achieved using spray pyrolysis (SP). Samples synthesized with various calcination temperatures and precursor concentrations indicated that the most suitable parameter for the synthesized powder is the calcination of 0.05 M Y3.92SiAlO8N:0.08Tb3+ at a temperature of 1600 °C. The effect of the selected parameters was substantiated by the high purity of the Y3.92SiAlO8N:0.08Tb3+ phase, as confirmed by X-ray diffraction (XRD) analysis. The Scherrer equation was used to calculate grain size. In addition, scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDS) confirmed the presence of micron-sized particles, which matched well with the theoretical chemical composition. The specific surface area of the phosphor powder was determined using the Brunauer–Emmett–Teller method. Finally, fluorescence spectrometry was used to determine the luminescence properties. The correlation between the crystallinity of the phosphor powder and narrowing emission is also discussed. [ABSTRACT FROM AUTHOR]

Barium tantalum oxynitride (BaTaO2N), as a member of an emerging class of perovskite oxynitrides, is regarded as a promising inorganic material for solar water splitting because of its small band gap, visible light absorption, and suitable band edge potentials for overall water splitting in the absence of an external bias. However, BaTaO2N still exhibits poor water‐splitting performance that is susceptible to its synthetic history, surface states, recombination process, and instability. This review provides a comprehensive summary of previous progress, current advances, existing challenges, and future perspectives of BaTaO2N for solar water splitting. A particular emphasis is given to highlighting the principles of photoelectrochemical (PEC) water splitting, classic and emerging photocatalysts for oxygen evolution reactions, and the crystal and electronic structures, dielectric, ferroelectric, and piezoelectric properties, synthesis routes, and thin‐film fabrication of BaTaO2N. Various strategies to achieve enhanced water‐splitting performance of BaTaO2N, such as reducing the surface and bulk defect density, engineering the crystal facets, tailoring the particle morphology, size, and porosity, cation doping, creating the solid solutions, forming the heterostructures and heterojunctions, designing the photoelectrochemical cells, and loading suitable cocatalysts are discussed. Also, the avenues for further investigation and the prospects of using BaTaO2N in solar water splitting are presented. [ABSTRACT FROM AUTHOR]

Nitride and hydride materials have been proposed as active supports for the loading of transition metal catalysts in thermal catalytic ammonia synthesis. However, the contribution of nitrogen or hydride anions in the support to the catalytic activity for supported transition‐metal catalysts is not well understood, especially for Fe‐based catalysts. Here, we report that hexagonal‐BaTiO3−xNy with nitrogen vacancies at face‐sharing sites acts as a more efficient support for Fe catalysts for ammonia synthesis than BaTiO3 or BaTiO3−xHx at 260 °C to 400 °C. Isotopic experiments, in situ measurements, and a small inverse isotopic effect in ammonia synthesis have revealed that nitrogen molecules are activated at nitrogen vacancies formed at the interface between Fe nanoparticles and the support. Nitrogen vacancies on BaTiO3−xNy can promote the activity of Fe and Ni catalysts, while electron donation and suppression of hydrogen poisoning by BaTiO3−xHx are significant in the Ru and Co systems. [ABSTRACT FROM AUTHOR]

A BaTaO2N (BTON) particulate photocatalyst enables solar water splitting in response to visible light irradiation at wavelengths of up to 640 nm. The specific nitridation conditions produced distinct types of BTON particles with the capability of one‐step overall water splitting (Active‐BTON) and without the overall water splitting activity (Inactive‐BTON). Unveiling the intrinsic differences between the active‐ and inactive‐BTON particles is crucial for obtaining more in‐depth information about the water splitting activity. Herein, we investigated the electrochemical (EC) and photoelectrochemical (PEC) properties of these BTON photocatalysts using the particulate‐based photoelectrodes for water splitting. EC measurements, including Mott–Schottky analysis, revealed that the flat band potential of Active‐BTON is located at a potential that is more positive than that of Inactive‐BTON, whereas the carrier concentration of Active‐BTON is one‐tenth lower than that of Inactive‐BTON. Irrespective of the pH value of the 1.0 M potassium phosphate aqueous solution, the Active‐BTON‐based photoelectrodes showed a higher photocurrent than that of Inactive‐BTON under simulated AM 1.5G solar illumination. The PEC performance of the BTON was found to be limited by the electrocatalytic activity of the CoOx co‐catalyst, specifically the electrolyte pH. [ABSTRACT FROM AUTHOR]

Spinel‐type lithium aluminum oxynitride (LiAlON) contains atomic disorders at every crystallographic position, including vacancies, cation, and anion disorders. In this work, the crystal structure of spinel‐type LiAlON with multiple atomic disorders was systematically studied by first‐principles calculation, solid‐state NMR, and the Rietveld crystal structure refinement. The theoretical simulations demonstrate that the Li+ occupies octahedral positions and prefers to be far away from the N3− and cation vacancies in the crystal structure of LiAlON. A spinel‐type LiAlON compound with chemical formula of Li0.06Al2.72O3.77N0.23 was prepared by solid‐state reaction. The local structure of Li+ and Al3+ was probed by 7Li and 27Al solid‐state NMR technology. Combined with theoretical calculations and solid‐state NMR, the crystal structure of Li0.06Al2.72O3.77N0.23 was fully resolved by the Rietveld refinement. This work provides a deep understanding on the disordered crystal structure of the spinel‐type LiAlON solid solution. [ABSTRACT FROM AUTHOR]

Tantalum oxynitride (TaOxN1−x) fibers were synthesized and evaluated for their electrocatalytic hydrogen activity using an in‐house developed centrifugal spinning setup. By tailoring the composition of the spinning solution and optimizing collector distance and rotation speed of the spinneret, bead‐free TaOxN1−x fibers with a diameter of 800 nm were obtained. The fibers were structurally characterized through phase and elemental analysis, confirming the formation of monoclinic TaOxN1−x with clear splitting of the X‐ray photoelectron spectroscopy peaks indicating Ta was in +5 oxidation state. The resulting oxynitride fibers exhibited superior electrocatalytic performance with low overpotentials (250 mV) to generate 10 mA/cm2 compared to Ta2O5 oxide fibers. Interestingly, the enhanced activity of oxynitride fibers was observed to be suppressed in basic medium due to the high oxophilicity of tantalum ions and a negative Gibbs adsorption‐free energy, leading to poisoning of the active sites. This work demonstrates a facile pathway for the fabrication of high‐performance electrocatalysts, based on TaOxN1−x fibers, from a cost‐effective and energy‐efficient centrifugal spinning technique. [ABSTRACT FROM AUTHOR]

Orange Eu2+‐doped phosphors are essential for light‐emitting diodes for cornering lights to prevent fatal road accidents at night, but such phosphors require features of high thermal, chemical stability and facile synthesis. This study reports a series of yellow‐orange‐red emitting SrAl2Si3ON6:Eu2+ oxynitride phosphors, derived from the SrAlSi4N7 nitride iso‐structure by replacing Si4+−N3− with Al3+−O2−. The introduction of a certain amount of oxygen enabled the facile synthesis under atmospheric pressure using the air‐stable raw materials SrCO3, Eu2O3, AlN and Si3N4. SrAl2Si3ON6 has a smaller band gap and lower structure rigidity than SrAlSi4N7 (5.19 eV vs 5.50 eV, Debye temperature 719 K vs 760 K), but exhibits higher thermal stability with 100 % of room temperature intensity remaining at 150 °C compared to 85 % for SrAlSi4N7. Electron paramagnetic resonance, thermoluminescence and density functional theory revealed that the oxygen vacancy electron traps compensated the thermal loss. Additionally, no decrease in emission intensity was found after either being heated at 500 °C for 2 hours or being immersed in water for 20 days, implying both of the thermal and chemical stability of SrAl2Si3ON6:Eu2+ phosphors. The strategy of oxynitride‐introduction from nitride promotes the development of low‐cost thermally and chemically stable luminescent materials. [ABSTRACT FROM AUTHOR]

The oxygen reduction and evolution reactions are considered the bottleneck in many electrochemical devices, i. e. fuel cells, water electrolyzers, and metal‐air batteries. The continuous focus has been on inventing and exploring cost‐effective and robust electrocatalysts. Few developed non‐precious metal/metal‐free materials, in fact, outperformed state‐of‐the‐art catalysts during the half‐cell study. However, most of these materials show limited activity during the full cell demonstration, restricting their deployment in commercial energy devices. In this direction, transition metal nitrides (TMNs) have emerged as a potential alternative with peculiar electronic properties and the ease of tuning their intrinsic as well as extrinsic properties. High hardness, refractory nature, d‐band modulation ability and comparatively lower energy for the nitride formation are the other motivations to explore their effectiveness in oxygen electrocatalysis. Considering this, the minireview attempts first to present the properties of catalytic interest, followed by the most viable synthesis approaches in nanoengineering of the TMNs. Next, we provide key trends toward catalytic property modulation for oxygen electrocatalysis, the role of TMNs as potential catalytic support, followed by the effect of TMNs′ in situ autoxidation on the performance. Finally, we state the current limitations of TMNs toward oxygen electrocatalysis, followed by our vision for further advancements. [ABSTRACT FROM AUTHOR]

This research manuscript investigates the structural and thermal stability of CrZrON coatings synthesized through reactive magnetron sputtering. The coatings were deposited at different temperatures with 120 °C and 400 °C, and with varying oxygen-to-reactive gas ratios in the range of 8.3% to 25.7%. The average chemical composition, crystallographic orientation, microstructure, lattice parameter, crystallite size, and hardness of the coatings were evaluated. The results revealed that the coatings deposited at a lower temperature of 120 °C exhibited a columnar structure, while those deposited at a higher temperature of 400 °C showed a transition towards a featureless or amorphous structure. The lattice parameter and crystallite size were influenced by the deposition temperature and oxygen ratio, indicating the incorporation of oxygen into the coatings. Hardness measurements demonstrated that the coatings' hardness decreased from 33.7 GPa to 28.6 GPa for a process temperature of 120 °C and from 32.1 GPa to 25.7 GPa for 400 °C with an increase in the oxygen ratio, primarily due to the formation of oxygen-rich compounds or oxides. Additionally, annealing experiments indicated that the coatings with featureless or amorphous structures exhibited improved thermal stability, as they maintained their structural integrity without delamination even at high annealing temperatures. [ABSTRACT FROM AUTHOR]

In this paper differences in chemical composition of ultra-thin silicon oxynitride layers fabricated in planar rf plasma reactor are studied. The ultra-thin dielectric layers were obtained in the same reactor by two different methods: ultrashallow nitrogen implantation followed by plasma oxidation and plasma enhanced chemical vapour deposition (PECVD). Chemical composition of silicon oxynitride layers was investigated by means of X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The spectroscopic ellipsometry was used to determine both the thickness and refractive index of the obtained layers. The XPS measurements show considerable differences between the composition of the fabricated layers using each of the above mentioned methods. The SIMS analysis confirms XPS results and indicates differences in nitrogen distribution.

Experiments presented in this work are a summary of the study that examines the possibility of fabrication of oxynitride layers for Si structures by nitrogen implantation from rf plasma only or nitrogen implantation from rf plasma followed immediately by plasma oxidation process. The obtained layers were characterized by means of: ellipsometry, XPS and ULE-SIMS. The results of electrical characterization of NMOS Al-gate test structures fabricated with the investigated layers used as gate dielectric, are also discussed.

The goal of this work was to study nitrogen implantation from plasma with the aim of applying it in dual gate oxide technology and to examine the influence of the rf power of plasma and that of oxidation type. The obtained structures were examined by means of ellipsometry, SIMS and electrical characterization methods.

History, beginning in the late 1960s during the Vietnam war, of the institutional changes that took place because of various military operations and the resulting changes in policies and requirements in the Department of Defense and the Army: Army Force XXI, DDRE, and Army After Next; this will include the evolution of personnel and vehicle protection materials and the impact of major DARPA programs. The new requirements emphasized light weight and changes in the basic research approach, which led to the approval of a strategic research objective, "Armor Materials by Design." At the same time, there were other National planning activities, workshops, and conferences advocating for the armor materials by design vision and the use of "figures of merit." The Army Research Laboratory responded to these initiatives by initiating an "Enterprise for Multiscale Research of Materials" leading to the funding of a revolutionary new collaborative research program on "materials in extreme dynamic environment." The role of the ARL Materials Center of Excellence will also be included. [ABSTRACT FROM AUTHOR]

Oxynitride 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. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) solar water splitting is favourable for transforming solar energy into sustainable hydrogen fuel using semiconductor electrodes. Perovskite-type oxynitrides are attractive photocatalysts for this application due to their visible light absorption features and stability. Herein, strontium titanium oxynitride (STON) containing anion vacancies of SrTi(O,N)3−δ was prepared via solid phase synthesis and assembled as a photoelectrode by electrophoretic deposition, and their morphological and optical properties and PEC performance for alkaline water oxidation are investigated. Further, cobalt-phosphate (CoPi)-based co-catalyst was photo-deposited over the surface of the STON electrode to boost the PEC efficiency. A photocurrent density of ~138 μA/cm at 1.25 V versus RHE was achieved for CoPi/STON electrodes in presence of a sulfite hole scavenger which is approximately a four-fold enhancement compared to the pristine electrode. The observed PEC enrichment is mainly due to the improved kinetics of oxygen evolution because of the CoPi co-catalyst and the reduced surface recombination of the photogenerated carriers. Moreover, the CoPi modification over perovskite-type oxynitrides provides a new dimension for developing efficient and highly stable photoanodes in solar-assisted water-splitting reactions. [ABSTRACT FROM AUTHOR]

The goal of this stydy was to explore the potential of the enhanced corrosion resistance of Ti(N,O) cathodic arc evaporation-coated 304L stainless steel using oxide nano-layers deposited by atomic layer deposition (ALD). In this study, we deposited Al2O3, ZrO2, and HfO2 nanolayers of two different thicknesses by ALD onto Ti(N,O)-coated 304L stainless steel surfaces. XRD, EDS, SEM, surface profilometry, and voltammetry investigations of the anticorrosion properties of the coated samples are reported. The amorphous oxide nanolayers homogeneously deposited on the sample surfaces exhibited lower roughness after corrosion attack compared to the Ti(N,O)-coated stainless steel. The best corrosion resistance was obtained for the thickest oxide layers. All samples coated with thicker oxide nanolayers augmented the corrosion resistance of the Ti(N,O)-coated stainless steel in a saline, acidic, and oxidising environment (0.9% NaCl + 6% H2O2, pH = 4), which is of interest for building corrosion-resistant housings for advanced oxidation systems such as cavitation and plasma-related electrochemical dielectric barrier discharge for breaking down persistent organic pollutants in water. [ABSTRACT FROM AUTHOR]

A series of β‐SiAlON:Eu2+ phosphors were synthesized from single‐source precursors, perhydropolysilazane chemically modified with Al(OCH(CH3)2)3, AlCl3, and EuCl2. The single‐source precursors were converted to β‐SiAlON:Eu2+ phosphors by pyrolysis under flowing N2 or NH3 at 1000°C, followed by heat treatment at 1800°C under an N2 gas pressure at 980 kPa. By varying the molar ratio of the chemical modifiers, β‐SiAlON:Eu2+ with the compositions close to the theoretical ones expressed as Si6−zAlzOz−2yN8−z+2y:yEu2+ were synthesized, where the z values and Eu2+ contents were controlled in the ranges of.44–.78 and.35–1.48 mol%, respectively. The polymer‐derived β‐SiAlON:Eu2+ phosphors exhibited green emission under excitation at 460 nm attributed to the 4f7–4f6(7f3)5d1 transition of dopant Eu2+. High‐angle annular dark‐field‐scanning transmission microscopy analysis confirmed that the doped‐Eu2+ existed interstitially within the channels along the c axis of host β‐SiAlON. Compared with the conventional powder metallurgy route, the polymer‐derived ceramic route in this study offers some advantages in the grain growth of host β‐SiAlON and photoluminescence properties in terms of green emission intensity under excitation at 460 nm, and the highest intensity was achieved for the polymer‐derived β‐SiAlON:Eu2+ with z =.64 and.37 mol% Eu2+. [ABSTRACT FROM AUTHOR]

Oxynitride 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. [ABSTRACT FROM AUTHOR]

The incorporation of a Luminescent down-shifting (LDS) layer has emerged as a compelling approach for augmenting the light absorption sensitivity and power conversion efficiency of solar cells, particularly in the short-wavelength light spectrum. In this investigation, we propose the utilization of low-cost, environmentally benign Boron carbon oxynitride (BCNO) phosphors as a viable material for the enhancement of solar radiation absorption in the ultraviolet-blue range. We synthesized BCNO phosphors through a combustion method and conducted a comprehensive analysis of the structural and spectral attributes concerning the impact of temperature. The synthesized boron carbon oxynitride phosphors exhibit a hexagonal boron nitride structure, with an irregular shape and an average particle size of 2447.9 nm. The analysis of photoluminescence spectra reveals that BCNO phosphors effectively capture photons within the 300–500 nm wavelength range and subsequently re-emit them at longer wavelengths. This phenomenon aligns with the overarching goal of optimizing solar cell performance, as it is in the longer wavelength range that solar cells exhibit enhanced efficiency. These findings support the promising potential of BCNO phosphors as a compelling choice for deployment as an LDS layer material on the periphery of solar cells. By facilitating increased photon absorption in the short-wavelength region, BCNO phosphors have the capacity to significantly enhance device performance.

Activation of narrow bandgap photocatalysts is a prerequisite for the efficient production of renewable hydrogen from water using sunlight. Loading of dual cocatalysts intended to promote reduction and oxidation reactions by photodeposition is known to greatly enhance the water splitting activity of certain oxide photocatalysts. However, it is difficult to photodeposit oxygen evolution cocatalysts onto narrow bandgap oxynitride photocatalysts because the driving forces for the necessary oxidation reactions are weak. The present work demonstrates oxidative photodeposition of the Fe-based cocatalyst FeOx onto a Mg-doped BaTaO2N photocatalyst having an absorption edge wavelength of 620 nm. This modification enhances the oxygen evolution activity of the photocatalyst more effectively than conventional impregnation methods. The rapid removal of photoexcited electrons from the photocatalyst by a reduction cocatalyst (Pt) and an electron acceptor (molecular oxygen) are evidently necessary for the photodeposition of the FeOx cocatalyst. A Mg-doped BaTaO2N photocatalyst coloaded with Pt and FeOx exhibits an apparent quantum yield of 1.2% at 420 nm during the oxygen evolution reaction in an aqueous AgNO3 solution. This photodeposition procedure does not involve any heat treatment and so provides new opportunities for the design and construction of oxygen evolution sites on narrow-bandgap non-oxide photocatalysts that may be prone to thermal decomposition. [ABSTRACT FROM AUTHOR]

We report the first synthesis of β‐SiAlON:Eu2+ phosphors from single‐source precursors, perhydropolysilazane (PHPS), chemically modified with Al(OCH(CH3)2)3, and EuCl2. The reactions occurring during the precursor synthesis and the subsequent thermal conversion of polymeric precursors into β‐SiAlON:Eu2+ phosphors have been studied by a complementary set of analytical techniques, including infrared spectroscopy, gas chromatography–mass spectrometry, thermogravimetry–mass spectrometry, X‐ray diffraction (XRD), photoluminescence spectroscopy, and scanning electron microscopy. It has been clearly established that Al(OCH(CH3)2)3 immediately reacted with PHPS to afford N–Al bonds at room temperature, whereas N–Eu bond formation was suggested to proceed above 600°C accompanied by the elimination of HCl up to 1000°C in flowing N2. The subsequent 1800°C‐heat treatment for 1 h under an N2 gas pressure at 980 kPa allowed converting the single‐source precursors into fine‐grained β‐SiAlON:Eu2+ phosphors. XRD analysis revealed that the Al/Si of.09 was the critical atomic ratio in the precursor synthesis to afford single‐phase β‐SiAlON (z =.55). Moreover, Eu2+‐doping was found to efficiently reduce the carbon impurity in the host β‐SiAlON. The polymer‐derived β‐SiAlON:Eu2+ phosphors exhibited green emission under excitation at 460 nm and achieved the highest green emission intensity at the critical dopant Eu2+ concentration at 1.48 at%. [ABSTRACT FROM AUTHOR]

Oxynitride or nitride photocatalysts are typically synthesized by heating oxide precursor particles at high temperatures under NH3 flow. Although there are numerous reports on optimizing the nitridation conditions for different materials, the detailed nitridation mechanism is still unclear. In this study, the nitridation of Ta2O5 to TaON was investigated. The degree of nitridation was quantitatively analyzed using the change in the weight of a powder after nitridation. Three regions were identified in the nitridation process for different nitridation times and NH3 flow rates. Moreover, the initial stage of the nitridation process (linear region) was formulated for the first time. Structural analysis, absorption properties, and oxygen evolution activity were combined with the degree of nitridation to reveal the relationship between the nitridation process and photocatalytic activity. The results of this work are useful for understanding and improving the photocatalytic properties of oxynitrides. [ABSTRACT FROM AUTHOR]

Solid solutions of strontium-tantalum oxynitride perovskite (SrTaO2N) and strontium-titanium oxide perovskite (SrTiO3) were prepared as possible candidates for novel inorganic pigments. The use of Ta-Ti binary oxide gel, which was obtained by the sol–gel method, was conducive to the development of single-phase solid solutions with a homogeneous atomic distribution. In addition, the use of urea as a nitriding agent availed to eliminate harmful ammonia gas during the synthesis. The color of solid solution depends on the band gap and Ti reduction state, which changes with Ti content. As a result, various chromatic colors, i.e., orange to yellow-green, were obtained from solid solutions. The solid solutions retained their color even after thermal and chemical resistance examinations. Because toxic substances were eliminated from the products and preparation process, the solid solutions show potentials to be applied as environmentally-friendly pigments. Highlights: Solid solutions of SrTaO2N and SrTiO3 were prepared by using alkoxide-derived metal oxide gels as precursors. The Ta-Ti binary oxide gel, wal, and thermal stabilities hich was prepared by co-condensation of Ta- and Ti-alkoxides, was suitable as a precursor compared with the mixture of Ta2O5 gel and TiO2 gel. Urea can be used as a solid nitriding agent to achieve ammonia-free synthesis of metal oxynitrides. Various chromatic colors were obtained from solid solutions by changing the Ti/Ta composition. [ABSTRACT FROM AUTHOR]

The development of new sintering processes for ferroelectric perovskite-type oxynitrides is a crucial aspect of realizing practical applications of these materials. The present study examined the sintering of SrTaO2N with B2O3, a new additive. The addition of B2O3 was found to significantly lower the sintering temperature. In addition, observations by transmission electron microscopy showed that the B2O3 combined with SrO to form an amorphous structure that enhances the diffusion of elements during high-temperature sintering.

The soil environment is one of the main places for the generation, emission, and absorption of various atmospheric pollutants, including nitrogen oxides (NOx) and volatile organic compounds (VOCs), which are the main chemical precursors for the formation of ground-level ozone. Ground-level ozone pollution has become a concerning environmental problem because of the harm it poses to human health and the surrounding ecological environment. However, current studies on chemical precursors of ozone mainly focus on emissions from industrial sources, forest vegetation, and urban vehicle exhaust; by contrast, few studies have examined the role of the soil environment on NOx and VOCs emissions. In addition, the soil environment is complex and heterogeneous. Agricultural activities (fertilization) and atmospheric deposition provide nutrients for the soil environment, with a significant effect on NOx and VOCs emissions. There is thus a need to study the environmental factors related to the release of NOx and VOCs in the soil to enhance our understanding of emission fluxes and the types of NOx and VOCs in the soil environment and aid efforts to control ground-level ozone pollution through appropriate measures such as management of agricultural activities. This paper reviews the generation of NOx and VOCs in the soil environment and the effects of various environmental factors on this process. Some suggestions are provided for future research on the regulation of NOx and VOCs emissions in the soil environment and the ability of the soil environment to contribute to ground-level ozone pollution.

Oxynitrides with the photoelectrochemical stability of oxides and desirable band energetics of nitrides comprise a promising class of materials for solar photochemistry. Challenges in synthesizing a wide variety of oxynitride materials has limited exploration of this class of functional materials, which we address using a reactive cosputtering combined with rapid thermal processing method to synthesize multi-cation-multi-anion libraries. We demonstrate the synthesis of a LaxTa1-xOyNz thin film composition spread library and its characterization by both traditional thin film materials characterization and custom combinatorial optical spectroscopy and X-ray absorption near edge spectroscopy (XANES) techniques, ultimately establishing structure-chemistry-property relationships. We observe that over a substantial La-Ta composition range the thin films crystallize in the same perovskite LaTaON2 structure with significant variation of anion chemistry. The relative invariance in optical band gap demonstrates a remarkable decoupling of composition and band energetics so that the composition can be optimized while retaining the desirable 2 eV band gap energy. We also demonstrate the intercalation of diatomic nitrogen into the La3TaO7 structure, which gives rise to a direct-allowed optical transition at 2.2 eV, less than half the value of the oxide's band gap. These findings motivate further exploration of the visible light response of this material that is predicted to be stable over a wide range of electrochemical potential.

Solid-state chemical transformations at the nanoscale can be a powerful tool for achieving compositional complexity in nanomaterials. It is desirable to understand the mechanisms of such reactions and characterize the local-level composition of the resulting materials. Here, we examine how reaction temperature controls the elemental distribution in (Ga1-xZnx)(N1-xOx) nanocrystals (NCs) synthesized via the solid-state nitridation of a mixture of nanoscale ZnO and ZnGa2O4 NCs. (Ga1-xZnx)(N1-xOx) is a visible-light absorbing semiconductor that is of interest for applications in solar photochemistry. We couple elemental mapping using energy-dispersive X-ray spectroscopy in a scanning transmission electron microscope (STEM-EDS) with colocation analysis to study the elemental distribution and the degree of homogeneity in the (Ga1-xZnx)(N1-xOx) samples synthesized at temperatures ranging from 650 to 900 °C with varying ensemble compositions (i.e., x values). Over this range of temperatures, the elemental distribution ranges from highly heterogeneous at 650 °C, consisting of a mixture of larger particles with Ga and N enrichment near the surface and very small NCs, to uniform particles with evenly distributed constituent elements for most compositions at 800 °C and above. We propose a mechanism for the formation of the (Ga1-xZnx)(N1-xOx) NCs in the solid state that involves phase transformation of cubic spinel ZnGa2O4 to wurtzite (Ga1-xZnx)(N1-xOx) and diffusion of the elements along with nitrogen incorporation. The temperature-dependence of nitrogen incorporation, bulk diffusion, and vacancy-assisted diffusion processes determines the elemental distribution at each synthesis temperature. Finally, we discuss how the visible band gap of (Ga1-xZnx)(N1-xOx) NCs varies with composition and elemental distribution.

Solid-state chemical transformations at the nanoscale can be a powerful tool for achieving compositional complexity in nanomaterials. It is desirable to understand the mechanisms of such reactions and characterize the local-level composition of the resulting materials. Here, we examine how reaction temperature controls the elemental distribution in (Ga1-xZnx)(N1-xOx) nanocrystals (NCs) synthesized via the solid-state nitridation of a mixture of nanoscale ZnO and ZnGa2O4 NCs. (Ga1-xZnx)(N1-xOx) is a visible-light absorbing semiconductor that is of interest for applications in solar photochemistry. We couple elemental mapping using energy-dispersive X-ray spectroscopy in a scanning transmission electron microscope (STEM-EDS) with colocation analysis to study the elemental distribution and the degree of homogeneity in the (Ga1-xZnx)(N1-xOx) samples synthesized at temperatures ranging from 650 to 900 °C with varying ensemble compositions (i.e., x values). Over this range of temperatures, the elemental distribution ranges from highly heterogeneous at 650 °C, consisting of a mixture of larger particles with Ga and N enrichment near the surface and very small NCs, to uniform particles with evenly distributed constituent elements for most compositions at 800 °C and above. We propose a mechanism for the formation of the (Ga1-xZnx)(N1-xOx) NCs in the solid state that involves phase transformation of cubic spinel ZnGa2O4 to wurtzite (Ga1-xZnx)(N1-xOx) and diffusion of the elements along with nitrogen incorporation. The temperature-dependence of nitrogen incorporation, bulk diffusion, and vacancy-assisted diffusion processes determines the elemental distribution at each synthesis temperature. Finally, we discuss how the visible band gap of (Ga1-xZnx)(N1-xOx) NCs varies with composition and elemental distribution.

We synthesized rock-salt-type Li–Ti oxynitride (LiTi n O x N y , n = 1 , 1.25, 1.5, 1.75, and 2) using solid-phase reaction. The best charge/discharge characteristics were obtained with a Ti/Li ratio of 1.25, and the maximum discharge capacity was 140 mAh/g. [ABSTRACT FROM AUTHOR]

Perovskite oxynitrides are an established class of photocatalyst materials for water splitting. Previous computational studies have primarily focused on their bulk properties and have drawn relevant conclusions on their light absorption and charge transport properties. The actual catalytic conversions, however, occur on their surfaces and a detailed knowledge of the atomic-scale structure and processes on oxynitride surfaces is indispensable to further improve these materials. In this contribution, we summarize recent progress made in the understanding of perovskite oxynitride surfaces, highlight key processes that set these materials apart from their pure oxide counterparts and discuss challenges and possible future directions for research on oxynitrides.

Solar‐powered one‐step‐excitation overall water splitting (OWS) using semiconducting materials is a simple means of achieving scalable and sustainable hydrogen production. While tantalum oxynitride (TaON) is one of the few photocatalysts capable of promoting OWS via single‐step visible‐light excitation, the efficiency of this process remains extremely poor. The present work employed 15 nm amorphous Ta2O5⋅3.3 H2O nanoparticles as a new precursor together with Zr doping and an optimized nitridation duration to synthesize a TaON‐based photocatalyst with reduced particle sizes and low defect densities. Upon loading with Ru/Cr2O3/IrO2 cocatalysts, this material exhibited stoichiometric water splitting into hydrogen and oxygen, with an order of magnitude improvement in efficiency. Our findings demonstrate the importance of inventing/selecting the appropriate synthetic precursor and of defect control for fabricating active OWS photocatalysts. [ABSTRACT FROM AUTHOR]

The development of new sintering processes for ferroelectric perovskite-type oxynitrides is a crucial aspect of realizing practical applications of these materials. The present study examined the sintering of SrTaO2N with B2O3, a new additive. The addition of B2O3 was found to significantly lower the sintering temperature. In addition, observations by transmission electron microscopy showed that the B2O3 combined with SrO to form an amorphous structure that enhances the diffusion of elements during high-temperature sintering. [ABSTRACT FROM AUTHOR]

A single crystal of Ba0.9Ce0.1LuAl0.2Si3.8N6.9O0.1 (barium cerium lutetium aluminosilicate nitride oxide) was obtained by heating a mixed powder of Ba3N2, Si3N4, Al, Lu2O3, and CeO2 at 2173 K for 1 h under N2 gas at 0.85 MPa. X-ray single-crystal structure analysis revealed that the title oxynitride is hexagonal (lattice constants: a = 6.0378 (5) Å, c = 9.8133 (9) Å; space group: P63mc) and isostructural with BaYbSi4N7. (Ba,Ce) and Lu atoms occupy twelvefold and sixfold coordination sites, respectively.