High-resolution X-ray Diffraction Research Articles

Effects of polyoxymethylene dimethyl ethers (PODEn) on soot characteristics in isooctane inverse diffusion flames

Polyoxymethylene dimethyl ethers (PODEn, n = 1–3) such as dimethoxymethane (DMM) and PODE3 are considered highly promising alternative fuels due to their lack of C–C bonds and significant oxygen contents. Particularly, PODE3-blends with diesel have been proven to substantially reduce soot emissions and fuel consumption rates under optimized engine conditions, although the impact on soot nanostructure properties remains unclear. This study explored the effects of DMM and PODE3 on soot characteristics in isooctane (i-octane) inverse diffusion flames, focusing on soot morphology, soot nanostructure, soot nanocrystallite, and soot spectral features. To compare soot particles behavior, DMM and PODE3 blended as the isooctane substitute (by 20% and 40% volumetric fractions) were examined with various diagnostic techniques, including high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS).The results showed that DMM and PODE3 contributed to a reduction in sooting tendency from i-octane flames, whereas the average soot mass decreased significantly as the PODE3 ratio increased, consistent with a higher oxygen concentration. Therefore, 20% PODE3/i-octane exhibited growing disorganized arrangements of soot particles with shorter fringes, smaller crystallite sizes, and a relatively lower degree of graphitization than 20% and 40% DMM additions. However, XPS analysis indicated that soot produced from PODE3/i-octane mixtures had less oxygen atoms because PODE3 has multiple –CH2O- chain groups that can convert oxygen into carbon monoxide with little soot production. Moreover, HRTEM, XRD, and Raman spectra analyses of 40% PODE3-doped flames confirmed an exceptional correlation with turbostratic soot structure, as manifested by the shortest fringe length, longest fringe tortuosity, more amorphous soot with the smallest crystallite dimensions, and least degree of graphitization.

Mg incorporation induced microstructural evolution of reactively sputtered GaN epitaxial films to Mg-doped GaN nanorods

Mg-doped GaN films/nanorods were grown epitaxially on c-sapphire by reactive co-sputtering of GaAs and Mg at different N2 percentages in Ar–N2 sputtering atmosphere. Energy dispersive x-ray spectroscopy revealed that the Mg incorporation increases with increase of Mg area coverage of GaAs target, but does not depend on N2 percentage. In comparison to undoped GaN films, Mg-doped GaN displayed substantial decrease of lateral conductivity and electron concentration with the initial incorporation of Mg, indicating p-type doping, but revealed insulating behaviour at larger Mg content. Morphological investigations by scanning electron microscopy have shown that the films grown with 2%–4% Mg area coverages displayed substantially improved columnar structure, compared to undoped GaN films, along with rough and voided surface features at lower N2 percentages. With increase of Mg area coverage to 6%, the growth of vertically aligned and well-separated nanorods, terminating with smooth hexagonal faces was observed in the range of 50%–75% N2 in sputtering atmosphere. High-resolution x-ray diffraction studies confirmed the epitaxial character of Mg-doped GaN films and nanorods, which displayed complete c-axis orientation of crystallites and a mosaic structure, aligned laterally with the c-sapphire lattice. The catalyst-free growth of self-assembled Mg-doped GaN nanorods is attributed to increase of surface energy anisotropy due to the incorporation of Mg. However, with further increase of Mg area coverage to 8%, the nanorods revealed lateral merger, suggesting enhanced radial growth at larger Mg content.

A Study on the Growth Conditions Role in Defining InGaAs Epitaxial Layer Quality

This study delves into the epitaxial growth and characterization of InxGa1-xAs layers on InP substrate, a critical area in the development of high-performance III-V semiconductor devices. InxGa1-xAs is renowned for its superior electron mobility and broad spectral response, making it indispensable in applications ranging from photodetectors to quantum cascade lasers. Employing a horizontal flow reactor MOVPE (metal-organic vapor phase epitaxy) technique, we meticulously grew n-InxGa1-xAs epilayers under varying conditions to investigate the impact of indium content, growth temperature, and V/III ratio on the material's structural, optical, and electrical properties. HRXRD (High-resolution X-ray diffraction) and Hall-effect measurements provided insights into the correlation between growth parameters and epitaxial layer quality, including dislocation density and carrier mobility. Our findings highlight the delicate balance required in the growth process to optimize the InxGa1-xAs /InP structure's performance for advanced semiconductor applications. The research underscores the potential of tailored InxGa1-xAs layers to push the boundaries of current photonics and optoelectronics technologies, emphasizing the importance of growth condition optimization for enhancing device efficiency and thermal stability.

Electronic structure of superconducting VN(111) films

Vanadium nitride (VN) is a transition-metal nitride with remarkable properties that have prompted extensive experimental and theoretical investigations in recent years. However, there is a current paucity of experimental research investigating the temperature-dependent electronic structure of single-crystalline VN. In this study, high-quality VN(111) films were successfully synthesized on α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha$$\\end{document}-Al2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}O3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document}(0001) substrates using magnetron sputtering. The crystal and electronic structures of the VN films were characterized by a combination of high-resolution X-ray diffraction, low-energy electron diffraction, resonant soft X-ray absorption spectroscopy, and ultraviolet photoelectron spectroscopy. The electrical transport measurements indicate that the superconducting critical temperature of the VN films is around 8.1 K. Intriguingly, the temperature-dependent photoelectron spectroscopy measurements demonstrate a weak temperature dependence in the electronic structure of the VN films, which is significant for understanding the ground state of VN compounds.

Growth, mechanical, thermal, electrical, linear, and nonlinear optical studies of urea resorcinol single crystals for NLO applications

Urea Resorcinol (UR) was synthesized and grown using the slow cooling technique to form a possible organic nonlinear optical crystal. Single crystal X-ray diffraction analysis was used to determine the shape and lattice characteristics of the generated UR crystals. The crystallinity was verified using a high-resolution X-ray diffraction examination. The emission and transparency of the formed crystal were revealed by optical studies including photoluminescence and UV–visible-NIR spectrum analyses. Through the use of an optical microscope and the Vickers microhardness tester, its mechanical behavior was investigated and the density of its etch pits was estimated. The investigations were also conducted on the UR crystal's microphysical properties, including its dielectric tensor, dielectric loss, and thermal analysis. An Nd:YAG laser was used to quantify the laser-induced surface damage and the results were connected to the grown crystal's specific heat capacity. By using the Kurtz and Perry technique, the efficiency of second harmonic generation was determined for different UR crystal particle sizes that have good phase matchability, and its SHG output was compared to urea.

MBE-grown tetragonal FeTe consisting of c-axis-aligned nanocrystals

Tetragonal FeTe grown on c-plane sapphire by the molecular beam epitaxy technique is found to result in a new structural phase consisting of c-axis-aligned nanocrystals. Their reflection high-energy electron diffraction patterns display two sets of streaks simultaneously at all rotation angles of the sample. High-resolution x-ray diffraction studies confirm that the nanocrystals are tetragonal FeTe with their c-axes aligned to the growth direction. Atomic force microscopy imaging reveals that further growth of these nanocrystals involves a cannibalism process resulting in nanocrystal pillars with sizes of about 0.5–1 µm. The temperature-dependent resistance of these thin films displays an overall semiconducting behavior, however, with a non-measurable state or jumps and falls depending on their nominal thickness, which can be attributed to the thermal responses of the nanocrystals during cooling and heating processes. This discovery provides an approach to form inhomogeneous heterostructures with all possible twisted angles.

Epitaxial growth and magnetic properties of kagome metal FeSn/elemental ferromagnet heterostructures

Binary kagome compounds TmXn (T = Mn, Fe, Co; X = Sn, Ge; m:n = 3:1, 3:2, 1:1) have garnered recent interest owing to the presence of both topological band crossings and flatbands arising from the geometry of the metal-site kagome lattice. To exploit these electronic features for potential applications in spintronics, the growth of high-quality heterostructures is required. Here, we report the synthesis of Fe/FeSn and Co/FeSn bilayers on Al2O3 substrates using molecular beam epitaxy to realize heterointerfaces between elemental ferromagnetic metals and antiferromagnetic kagome metals. Structural characterization using high-resolution x-ray diffraction, reflection high-energy electron diffraction, and electron microscopy reveals that the FeSn films are flat and epitaxial. Rutherford backscattering spectroscopy was used to confirm the stoichiometric window where the FeSn phase is stabilized, while transport and magnetometry measurements were conducted to verify metallicity and magnetic ordering in the films. Exchange bias was observed, confirming the presence of antiferromagnetic order in the FeSn layers, paving the way for future studies of magnetism in kagome heterostructures and potential integration of these materials into devices.

Highly oriented crystalline si on epitaxial Gd2O3/Si(111) substrate using low-cost Radio Frequency sputtering for Silicon on Insulator application

Silicon-on-Insulator (SOI) technology has been the center of attraction with the advancement in Radio Frequency (RF) technology and the advent of Internet-of-Things due to its low-power operation with reduced parasitic and short-channel effects. However, the state-of-the-art smart-cut method used for the SOI wafer is costly. Alternatively, the notion of using the Si channel layer on epitaxial rare-earth oxide has been proposed. In literature, the existing techniques used to achieve the same, such as Molecular beam Epitaxy or reduced-pressure chemical vapor deposition technique, are either costly or non-high-volume manufacturable. In this context, we propose a method to fabricate the highly oriented crystalline Si(111) channel layer (Top-Si) on an epitaxial Gd2O3/Si(111) virtual substrate (SOXI) utilizing the solid phase epitaxy using the high-volume manufacturing friendly (HVM), low-cost RF magnetron sputtering technique. First, we have shown the multicrystalline Si and epitaxial Gd2O3 layer grown on Si(111) substrate, as confirmed using high-resolution X-ray diffraction (HRXRD) and Transmission Electron Microscopy (TEM). Second, we investigated the impact of rapid thermal annealing at 850 °C on the heterostructure using HRXRD and TEM. It is observed that the high-temperature annealing transforms the Top-Si layer into the highly oriented crystalline Si(111) layer by fusing smaller grains towards larger grains. Hence, we demonstrate a low-cost, HVM-friendly technique for the fabrication of SOXI wafers.

Effect of substrate on structural and transport properties of La0.05Sr0.95SnO3 and La0.05Ba0.95SnO3 epitaxial films

Perovskite-structured stannate La0.05Sr0.95SnO3 and La0.05Ba0.95SnO3 films were deposited on SrTiO3, LaAlO3, LSAT, PMN-PT, and MgO substrates using pulsed laser deposition, respectively. The effects of substrates on the structure, transport properties, and optical properties of the films were investigated in detail. High-resolution X-ray diffraction results revealed the epitaxial growth of all films on each substrate without any impurity phase, and a high lattice quality indicated by the rocking curves. Atomic force microscopy images confirmed the low root-mean-square roughness observed in all films. Hall effect measurements showed that the maximum mobility was obtained for both La0.05Sr0.95SnO3 films and La0.05Ba0.95SnO3 films grown on SrTiO3 substrates, with values of 26.46 cm2/Vs and 43.09 cm2/Vs, respectively. The temperature dependence of resistivity at low temperatures was attributed to e−-e− interactions. Optical transmittance spectra showed high transparency of all films in both visible and near-infrared regions. Collectively, these results indicate that La-doped SrSnO3 and BaSnO3 films exhibit excellent performance across various substrates, providing a wide range of options for optoelectronic device applications.

Structural and magnetic properties of Ni cluster embedded (111)NiO layers grown on (0001)GaN films

(111) NiO epitaxial layers embedded with crystallographically oriented Ni-clusters are grown on c-GaN/Sapphire templates using the pulsed laser deposition technique. Structural and magnetic properties of the films are examined by a variety of techniques including high-resolution x-ray diffraction, precession-electron diffraction, and superconducting quantum interference device magnetometry. It has been found that Ni-clusters are formed in the NiO matrix only at sufficiently low oxygen pressures during the growth. The study further reveals that the orientation, shape, size, density, and magnetic properties of these clusters depend strongly on the growth temperature (TG). Although most of the Ni-clusters are found to be obtained crystallographically aligned with the NiO matrix with Ni(111) ∥NiO(111), clusters with other orientations also exist, especially in samples grown at lower temperatures. The average size and density of the clusters increase with TG. The proportion of the Ni(111) ∥ NiO(111)-oriented clusters also improves as TG is increased. All cluster embedded films show ferromagnetic behavior even at room temperature. Easy-axis is found to be oriented in the layer plane in samples grown at relatively lower temperatures. However, it turns perpendicular to the layer plane for samples grown at sufficiently high temperatures. This reversal of easy-axis has been attributed to the size dependent competition between the shape and magnetoelastic and the surface anisotropies of the clusters. This composite material thus has great potential to serve as a spin-injector and spin-storage medium in GaN-based spintronics of the future.

Defect accumulation in β-Ga2O3 implanted with Yb

Radiation-induced crystal lattice damage and its recovery in wide bandgap oxides, in particular beta-gallium oxide (β-Ga2O3), is a complex process. This paper presents the detailed study of defect accumulation in the β-Ga2O3 single crystal implanted with Ytterbium (Yb) ions and the impact of Rapid Thermal Annealing (RTA) on the defects formed. The (2¯01)oriented β-Ga2O3 single crystals were implanted with eleven fluences of Yb ions ranging from 1 × 1012 to 5 × 1015 at/cm2. Channeling Rutherford Backscattering Spectrometry (RBS/c) was used to study the crystal lattice damage induced by ion implantation and the level of structure recovery after annealing. The quantitative and qualitative analyses of collected spectra were performed by computer simulations. As a result, we present the first defect accumulation curve of β-Ga2O3 implanted with rare earth ion that reveals a two-step damage process. In the first stage, the damage of the β-Ga2O3 is inconspicuous, but begins to grow rapidly from the fluence of 1 × 1013 at/cm2, reaching the saturation at the random level for the Yb ion fluence of 1 × 1014 at/cm2. Further irradiation causes the damage peak to become bimodal, indicating that at least two new defect forms develop for the higher ion fluence. These two damage zones differently react to annealing, suggesting that they could origin from two phases, the amorphization phase and the new crystalline phase of Ga2O3. High-resolution x-ray diffraction (HRXRD) demonstrates the presence of strain and the γ phase of Ga2O3 after implantation, which disappear after annealing.

Similarities and differences among selected gemmological varieties of chalcedony: chemistry, mineralogy and microstructure

AbstractThis study describes a new variety of chalcedony with a unique inhomogeneous bluish green hue, named aquaprase. It was discovered in Africa and is considered to be a valuable addition to the gem trade. A multi-methodological approach was used to examine its chemistry, mineralogy and microstructure, which were then compared to those of chrysoprase and agate, two of the most popular varieties of chalcedony. Optical microscopy revealed a complex microstructural heterogeneity in the different colour intensity areas/bands of aquaprase and agate, whereas chrysoprase exhibited a more homogeneous coexistence of micro- and cryptocrystalline quartz. High-resolution synchrotron XRD was essential for highlighting the complex assemblage of various types of α-quartz in aquaprase and agate (which differ in terms of crystal size and/or cell parameters). Micro-Raman spectroscopy revealed α-quartz and moganite in all three varieties of chalcedony and the presence of the nickel-bearing layered silicate mineral, willemseite, in chrysoprase, which is responsible for its green colouration. The chemical analysis displayed a homogeneous composition of agate, as well as high levels of nickel content in the chrysoprase variety. Aquaprase showed significant amounts (ppm by weight) of trace elements (Al, Mg, Na, K, Ca, Ti, U and Fe) characteristic of its formation environment, as well as high values of Cr, which are thought to be the cause of its bluish green colouration.

Characterization of single-crystal phenothiazine synthesized using the vertical Bridgman method

Abstract A bulk organic single crystal of phenothiazine measuring 65 mm in length and 10 mm in width was grown using the single zone vertical Bridgman technique (VBT), which was visible to the naked eye. Powder X-ray diffraction, also known as XRD, was used in order to perform crystal structural verification on the manufactured crystal. The Fourier transform infrared spectroscopy (FT-IR) approach was used in order to ascertain the crystals’ respective vibrational frequencies. In order to evaluate the single crystal’s crystalline perfection and optical quality, high-resolution X-ray diffraction rocking curve measurement (HRXRD) and UV transmittance spectrum analysis were used. So as to investigate the nonlinear optical (NLO) activity of the generated single crystals, a Q-switched and pulsed Nd: YAG laser was used in the research. This led to the discovery of the SHG efficiency. The single crystal’s mechanical strength was evaluated using Vicker’s microhardness measurement, which provided an approximation of the true value. Furthermore, the single crystal was examined and reported for its optical birefringence, photoluminescence, and refractive index.

Synthesis, structural, optical, and thermal properties of LaFeO3/Poly(methyl methacrylate)/Poly(vinyl acetate) nanocomposites for radiation shielding

This work is an attempt to develop flexible radiation shielding based on a blend of polymethyl methacrylate (PMMA)/polyvinyl acetate (PVAc) and LaFeO3 nanoparticles (NPs). LaFeO3 and LaFeO3/PMMA/PVAc were made using simple chemical techniques. A high-resolution transmission electron microscope (HR-TEM) and X-ray diffraction (XRD) showed that well-crystallized LaFeO3 NPs with particles 79 nm in size and an orthorhombic shape were obtained. In addition, XRD confirmed the existence of PMMA, PVAc, and LaFeO3 in the nanocomposite films. Fourier transform infrared (FTIR) confirmed that the LaFeO3 NPs and the reactive functional groups in the blend interacted with each other. Field emission-scan electron microscope (FE-SEM) analysis showed that PMMA and PVAc form a homogenous blend and that the LaFeO3 NPs were spread out inside and on the blend surface. The samples showed transmittance in the range of 30–74% and a small extinction coefficient (≤ 0.08). The samples exhibited a dual-band gap structure, and the direct (indirect) band gap shrank from 5.1 to 4.7 eV (4.9 to 4.4 eV). The thermal analyses showed that the samples are thermally stable up to 260 °C. The Phy-X/PSD software was used to figure out the theoretical gamma-ray attenuation parameters, such as the mass attenuation coefficient, the mean free path, and the half-value layer, for different PMMA/PVAc + x% LaFeO3 composites. It is demonstrated that the PMMA/PVAc + 10 wt% LaFeO3 sample exhibits much better shielding effectiveness than PMMA/PVAc, and hence it is suitable for protecting against radiation.

Shock-induced dissociation of soda-lime glass and the formation of single crystals of quartz and polycrystalline silicon

Amorphous soda-lime glass was subjected to shock induced loading with velocities of the impactor ∼10 km/s. The recovered sample was analyzed using high resolution x-ray diffraction and cross-polarized microscopy. The recovered samples were in form of aggregate consisting of the crystalline phases, polycrystalline alpha quartz, and silicon, which were identified in x-ray diffraction scans. We demonstrate high velocity impacts result in the transformation of amorphous glass to single crystalline quartz as a alpha-phase, and shock induced dissociation of silica into Si. In addition, a trace amount of tetragonal stishovite phase, which is extremely hard high-pressure phase of silicon dioxide, has been observed. This provides a new insight in understanding materials transformation behavior under extreme conditions. This will also contribute to our understanding of astronomical phenomenon, including meteorite and asteroid impacts on Earth and Earth-like planets.

Elastic and inelastic strain in submicron-thick ZnO epilayers grown on r-sapphire substrates by metal-organic vapour phase deposition.

A significant part of the present and future of optoelectronic devices lies on thin multilayer heterostructures. Their optical properties depend strongly on strain, being essential to the knowledge of the stress level to optimize the growth process. Here the structural and microstructural characteristics of sub-micron a-ZnO epilayers (12 to 770 nm) grown on r-sapphire by metal-organic chemical vapour deposition are studied. Morphological and structural studies have been made using scanning electron microscopy and high-resolution X-ray diffraction. Plastic unit-cell distortion and corresponding strain have been determined as a function of film thickness. A critical thickness has been observed as separating the non-elastic/elastic states with an experimental value of 150-200 nm. This behaviour has been confirmed from ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy measurements. An equation that gives the balance of strains is proposed as an interesting method to experimentally determine this critical thickness. It is concluded that in the thinnest films an elongation of the Zn-O bond takes place and that the plastic strained ZnO films relax through nucleation of misfit dislocations, which is a consequence of three-dimensional surface morphology.

Synthesis and Spectroscopic Characterization of Schiff Base Metal Complexes, Biological Activity, and Molecular Docking Studies.

New cobalt(II), copper(II), and zinc(II) Schiff metal complexes were synthesized by the condensation reaction of 4-nitrobenzene-1,2-diamine with 3-4-(diethylamino)-2-hydroxybenzaldehyde. Fourier transform infrared, nuclear magnetic resonance, ultraviolet-visible, electron paramagnetic resonance, and high-resolution electrospray ionization mass spectrometry and powder X-ray diffraction were used to characterize the synthesized H2L and its metal complexes. Conductance measurements, magnetic moment estimation, and metal estimation have all been determined and discussed. The electrochemical properties of the synthesized compounds have been determined and discussed using cyclic voltammetry. The molecular structures of H2L and its metal complexes have been optimized using the B3LYP functional and the 6-31G (d,p) basis set, and their parameters have been discussed. The quantum chemical properties of these synthesized compounds have been predicted through charge distribution and molecular orbital analysis. The biological properties of the synthesized compounds' antioxidant, antifungal, and antibacterial activity have been studied and discussed. Furthermore, H2L and its complexes have been docked with HER2-associated target proteins in breast cancer.

Hybrid Molecular Beam Epitaxy for Single-Crystalline Oxide Membranes with Binary Oxide Sacrificial Layers.

The advancement in thin-film exfoliation for synthesizing oxide membranes has led to possibilities for creating artificially assembled heterostructures with structurally and chemically incompatible materials. The sacrificial layer method is a promising approach to exfoliate as-grown films from a compatible material system, allowing for their integration with dissimilar materials. Nonetheless, the conventional sacrificial layers often possess an intricate stoichiometry, thereby constraining their practicality and adaptability, particularly when considering techniques such as molecular beam epitaxy (MBE). This is where easy-to-grow binary alkaline-earth-metal oxides with a rock salt crystal structure are useful. These oxides, which include (Mg, Ca, Sr, Ba)O, can be used as a sacrificial layer covering a much broader range of lattice parameters compared to conventional sacrificial layers and are easily dissolvable in deionized water. In this study, we show the epitaxial growth of the single-crystalline perovskite SrTiO3 (STO) on sacrificial layers consisting of crystalline SrO, BaO, and Ba1-xCaxO films, employing a hybrid MBE method. Our results highlight the rapid (≤5 min) dissolution of the sacrificial layer when immersed in deionized water, facilitating the fabrication of millimeter-sized STO membranes. Using high-resolution X-ray diffraction, atomic-force microscopy, scanning transmission electron microscopy, impedance spectroscopy, and scattering-type near-field optical microscopy (SNOM), we demonstrate single-crystalline STO membranes with bulk-like intrinsic dielectric properties. The employment of alkaline earth metal oxides as sacrificial layers is likely to simplify membrane synthesis, particularly with MBE, thus expanding the research and application possibilities.

Shock-wave-induced variation in structural, optical and third-order nonlinear properties of an L-ascorbic acid single crystal

The utilization of shock waves plays a pivotal role in the advancement of multiple scientific domains like aerospace, defense, geology, environment, medicine and many more. They serve as essential tools in scientific investigations, enabling the exploration of material behavior under extreme conditions, viz. elevated pressure and temperature. The present study is specifically dedicated to scrutinizing the repercussions of shock waves on an L-ascorbic acid single crystal, to which they were intentionally applied to assess their influence on structural, optical and third-order nonlinearity properties. Powder X-ray diffraction analysis unveiled a discernible overall enhancement in the crystalline quality of the grown crystal following exposure to shock waves. This observation was consistently corroborated by high-resolution X-ray diffraction data, particularly on the (200) crystallographic planes. Furthermore, the optical transmittance of the crystal exhibited a notable increase upon the application of shock waves, while the material's band gap remained unaffected. In parallel, the third-order nonlinearity of the crystal was found to undergo a significant augmentation as a consequence of the shock treatment, as confirmed through Z-scan measurements. These empirical findings unequivocally demonstrate the substantial enhancement in the structural, optical and nonlinear properties of the grown crystal when subjected to shock waves, rendering it well suited for nonlinear optical applications.

Mechanistically Guided Materials Chemistry: Synthesis of Ternary Nitrides, CaZrN2 and CaHfN2.

Recent computational studies have predicted many new ternary nitrides, revealing synthetic opportunities in this underexplored phase space. However, synthesizing new ternary nitrides is difficult, in part because intermediate and product phases often have high cohesive energies that inhibit diffusion. Here, we report the synthesis of two new phases, calcium zirconium nitride (CaZrN2) and calcium hafnium nitride (CaHfN2), by solid state metathesis reactions between Ca3N2 and MCl4 (M = Zr, Hf). Although the reaction nominally proceeds to the target phases in a 1:1 ratio of the precursors via Ca3N2 + MCl4 → CaMN2 + 2 CaCl2, reactions prepared this way result in Ca-poor materials (CaxM2-xN2, x < 1). A small excess of Ca3N2 (ca. 20 mol %) is needed to yield stoichiometric CaMN2, as confirmed by high-resolution synchrotron powder X-ray diffraction. In situ synchrotron X-ray diffraction studies reveal that nominally stoichiometric reactions produce Zr3+ intermediates early in the reaction pathway, and the excess Ca3N2 is needed to reoxidize Zr3+ intermediates back to the Zr4+ oxidation state of CaZrN2. Analysis of computationally derived chemical potential diagrams rationalizes this synthetic approach and its contrast from the synthesis of MgZrN2. These findings additionally highlight the utility of in situ diffraction studies and computational thermochemistry to provide mechanistic guidance for synthesis.