X-ray Diffraction Measurements Research Articles

X-ray Characterizations of Exfoliated MoS2 Produced by Microwave-Assisted Liquid-Phase Exfoliation

An X-ray analysis of exfoliated MoS2, produced by means of microwave-assisted liquid-phase exfoliation (LPE) from bulk powder in 1-methyl-2-pyrrolidone (NMP) or acetonitrile (ACN) + 1-methyl-2-pyrrolidone (NMP) solvents, has revealed distinct structural differences between the bulk powder and the microwave-exfoliated samples. Specifically, we performed X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements to identify the elements of our exfoliated sample deposited on a Si substrate by drop-casting, as well as their chemical state and its structural crystalline phase. In the exfoliated sample, the peaks pattern only partially resemble the theoretical Miller indices for MoS2. In contrast, the bulk powder’s spectrum shows the characteristic peaks of the 2H polytype of MoS2, but with some broadening. Notable is the retention of partial crystallinity in the post-exfoliation phases, specifically in the normal-to-plane orientation, thus demonstrating the effectiveness of microwave-assisted techniques in producing 2D MoS2 and attaining desirable properties for the material. XPS measurements confirm the success of the exfoliation procedure and that the exfoliated sample retains its original structure. The exfoliation process has been optimized to maintain the structural integrity of MoS2 while enhancing its surface area and electrochemical performance, thereby making it a promising material for advanced electronic and optoelectronic applications ranging from energy storage to sensing devices under ambient conditions.

Characterization of the lattice preferred orientation of hcp iron transformed from the single-crystal bcc phase in situ at high pressures up to 80 GPa

Studying the anisotropic physical properties of hexagonal closed-packed (hcp) iron is essential for understanding the properties of the Earth’s inner core related to the preferred orientation of the inner core materials suggested by seismic observations. Investigating the anisotropic physical properties of hcp iron requires (1) the synthesis of hcp iron samples that exhibit several distinctive types of strong lattice preferred orientation (LPO) and (2) the quantitative LPO analysis of the samples. Here, we report the distinctive LPO of hcp iron produced from single-crystal body-centered cubic (bcc) iron compressed along three different crystallographic orientations ([100], [110], and [111]) in a diamond anvil cell based on synchrotron multiangle X-ray diffraction measurements up to 80 GPa and 300 K. The orientation relationships between hcp iron and bcc iron are consistent with the Burgers orientation relationship with variant selection. We show that the present method is a way to synthesize hcp iron with strong and characteristic LPO, which is beneficial for experimentally evaluating the anisotropic physical properties of hcp iron.

6-(6-Methyl-1,2,4,5-Tetrazine-3-yl)-2,2'-Bipyridine: A N-Donor Ligand for the Separation of Lanthanides(III) and Actinides(III).

Here, we report the synthesis of the 6-(6-methyl-1,2,4,5-tetrazine-3-yl)-2,2'-bipyridine (MTB) ligand that has been developed for lanthanide/actinide separation. A multimethod study of the complexation of MTB with trivalent actinide and lanthanide ions is presented. Single-crystal X-ray diffraction measurements reveal the formation of [Ce(MTB)2(NO3)3], [Pr(MTB)(NO3)3H2O], and [Ln(MTB)(NO3)3MeCN] (Ln = Nd, Sm, Eu, Gd). In addition, the complexation of Cm(III) with MTB in solution was studied by time-resolved laser fluorescence spectroscopy. The results show the formation of [Cm(MTB)1-3]3+ complexes, which occur in two different isomers. Quantum chemical calculations reveal an energy difference between these isomers of 12 kJ mol-1, clarifying the initial observations made by time-resolved laser fluorescence spectroscopy (TRLFS). Furthermore, quantum theory of atoms in molecules (QTAIM) analysis of the Cm(III) and Ln(III) complexes was performed, indicating a stronger covalent contribution in the Cm-N interaction compared to the respective Ln-N interaction. These findings align well with extraction data showing a preferred extraction of Am and Cm over lanthanides (e.g., max. SFAm/Eu = 8.3) at nitric acid concentrations <0.1 mol L-1 HNO3.

Analysis of CeO2/SiO2 double-layer thin film stack with antireflection effect for silicon solar cells

This study introduces CeO2/SiO2 double-layer film stacks and its antireflection coating effect. Optical properties were analyzed by spectrophotometer measurements; surface morphology and cross-sections were observed by Scanning Electron Microscopy (SEM); elemental distributions and crystallographic properties were determined by Energy Dispersive Spectroscopy (EDS) and X-ray Diffraction (XRD) measurements. Average reflectance of single-layer 0.3MSiO2, 0.6MSiO2, and 0.3MCeO2 thin films were 30.54%, 20.12%, and 14.23%, respectively. Average reflectance was decreased significantly down to 5.9% by 0.3MCeO2/0.6MSiO2 double-layer thin films comparing to those of the results of single-layer films and bare silicon surface reflection (~40%). Antireflective effect of the films on solar cells was estimated by simulation using the measured reflection data. Simulated solar cells indicate that 0.3MCeO2/0.6MSiO2 double-layer antireflective coatings are capable to increase the efficiency significantly and conversion efficiency of 21.7% could be achieved.

Phonon-assisted leakage current of InGaN light emitting diode

Abstract We report on the leakage current mechanism in a blue GaN-based light-emitting diode (LED). The device structure was grown by the MOCVD technique on a sapphire substrate. The LED was characterized through various measurements including current-voltage, electroluminescence, and secondary ion mass spectroscopy (SIMS). Capacitance-voltage measurements were employed to calculate the depletion layer thickness at different bias voltages and analyze the doping profile in the active layer. The reverse temperature-dependent current-voltage measurements were carried out to study the leakage mechanism. The leakage current was explained by phonon-assisted tunneling of charge carriers through deep trap states. The trap energy and density of states were extracted from the application of the introduced model. Cathodoluminescence measurements were performed to evaluate the density of dislocations, which were then compared to X-ray diffraction measurements. The determined value was close to the density of states obtained from the tunneling model.

Influence of calcination temperature and particle size distribution on the physical properties of SrFe12O19 and BaFe12O19 hexaferrite powders

The paper deals with the economic optimisation of ferrite powder preparation during producing hard ferrite magnets. The magnetic properties of ferrites are investigated by replacing feedstock and reducing calcination temperature and particles in the order of tens of microns. The granulates about 8–10 mm in size were calcined for 2 h in the temperature range from 1100 °C to 1300 °C and additionally crushed and milled to an average particle size of about 80–90 µm. The scanning electron microscopy images confirmed the agglomerates of particles with different shapes and sizes in tens of µm. The X-ray diffraction measurements revealed that, besides the SrFe12O19 and BaFe12O19 phases, there was also the presence of 2–39% hematite. The highest values of maximum energy product (BH)max = 930 J/m3 and remanent magnetic induction Br = 72.8 mT were obtained at a calcination temperature of 1300 °C. The Henkel plots confirmed the presence of exchange-coupling and dipolar magnetic interactions at lower and higher magnetic fields, respectively. The strength of interactions was also dependent on the calcination temperature. Replacing strontium with barium led to a deterioration of the magnetic parameters, which were optimal at a lower calcination temperature (1100 °C). This phenomenon was partly overcome by reducing the mean particle size of Ba-based hexaferrites to 45–50 µm.

Design of FDM fabricated poly-lactic acid parts with forced-air cooling speed as the new control parameter to tune its shape memory effect

Poly lactic acid (PLA) as one of the shape memory polymers has extensively been used as the material in the 3D printing by fused deposition modeling process. In this study, we introduced the forced-air cooling speed as new control parameter in the fabrication process. A commercial material extrusion printer was retrofitted with a control module of forced-air cooling system. The shape memory effects of the PLA printed in different cooling speeds from 0–5 m s−1 were first measured by submerging the printed coupon specimens into water bath at recovery temperature. It is found that the changes in dimensions were mainly anisotropic and dependent of the raster angle in printing, in addition to the controlled cooling speed. The shape memory strains were roughly in linear trend with the magnitude of cooling air speed. In other words, the shape memory effect of the PLA can be easily controlled by the cooling air speed in fabrication. X-ray diffraction measurement on the specimens before and after recovery treatment confirmed the shape memory effect was related to the partial crystallization of molecular structure. Moreover, the different cooling air speeds also induced different thermal stresses in the printed specimens which manifest its important role in the total shape memory strain. Finally, the proposed theoretical beam formulation for the recovery bending deflection was shown to have good prediction accuracy comparing with experimental measurements.

Effects of K excess in microstructure of (Ba0.6K0.4)Fe2As2 superconducting powders

Abstract Iron-based superconductors (IBSs) are promising for high-field applications due to their exceptional characteristics, like ultrahigh upper critical field and minimal electromagnetic anisotropy. Creating multifilamentary superconducting wires with elevated transport critical current density is essential for practical use. The Powder in Tube (PIT) technique is commonly used for this purpose, but achieving optimal results requires careful exploration of powder microstructural properties. This is particularly crucial for superconductors like (Ba,K)122, the IBS most promising from an applicative point of view, where factors such as reactivity, volatility, and toxicity of constituent elements affect phase formation.&amp;#xD;Potassium volatility often leads to nonstoichiometric conditions, introducing excess potassium in the formulation. This study focuses on the impact of potassium excess δ on the microstructural properties of the 'optimally doped' (Ba0.6K0.4+δ)Fe2As2 phase (0≤δ≤0.08). Using techniques like Scanning Electron Microscopy (SEM), X-ray diffraction, and temperature-dependent magnetization measurements, we demonstrate the ability to produce nearly pure powders of the superconducting phase with controlled grain size. Our findings are relevant for PIT wire fabrication, where grain size strongly affects mechanical deformation. Grain size also influences transport properties, as observed in previous studies, where reducing grain size enhanced current-carrying capability at high magnetic fields.&amp;#xD;

Pinpointing lattice-matched conditions for wurtzite ScxAl1−xN/GaN heterostructures with x-ray reciprocal space analysis

Using comprehensive x-ray reciprocal space mapping, we establish the precise lattice-matching composition for wurtzite ScxAl1−xN layers on (0001) GaN to be x = 0.14 ± 0.01. 100 nm thick ScxAl1−xN films (x = 0.09–0.19) were grown in small composition increments on c-plane GaN templates by plasma-assisted molecular beam epitaxy. The alloy composition was estimated from the fit of the (0002) x-ray peak positions, assuming the c-lattice parameter of ScAlN films coherently strained on GaN increases linearly with Sc-content determined independently by Rutherford backscattering spectrometry [Dzuba et al., J. Appl. Phys. 132, 175701 (2022)]. Reciprocal space maps obtained from high-resolution x-ray diffraction measurements of the (101¯5) reflection reveal that ScxAl1−xN films with x = 0.14 ± 0.01 are coherently strained with the GaN substrate, while the other compositions show evidence of relaxation. The in-plane lattice-matching with GaN is further confirmed for a 300 nm thick Sc0.14Al0.86N layer. The full-width-at-half-maximum of the (0002) reflection rocking curve for this Sc0.14Al0.86N film is 106 arc sec and corresponds to the lowest value reported in the literature for wurtzite ScAlN films.

Highlighting amorphous phase separation process on cooling borosilicate melts using impedance spectroscopy

Four samples of sodium borosilicate glasses of composition (100 - x)(SiO2 - B2O3) - xNa2O with x = 4, 7, 10 and 25 mol% were synthesized and studied in a wide temperature range (up to 1673 K) using impedance spectroscopy, from the molten to the solid states. During melt cooling of three compositions (x = 4, 7 and 10), a clear transition was observed on the conductivity behavior at a critical temperature (Tcrit ≈ 973 K), highlighting the onset of an amorphous phase separation, in agreement with both Differential Scanning Calorimetry thermograms and literature. The amorphous nature of the phase separated samples was verified by in situ X-Ray Diffraction measurements performed under the same thermal conditions. Furthermore, Scanning Electron Microscopy micrographs taken on these three samples at room temperature after the impedance measurement confirmed the presence of two different phases, whose size and morphology vary with composition. As expected, the x = 25 sample did not show phase separation and remained homogeneous down to room temperature.

A single phased full color emitting pyrochlore type phosphor La2Y0.66Sn0.66Sb0.66O7: Bi3+, Eu3+ for white light emitting diode applications (WLEDs)

The phosphor converted white light emitting diodes (pc-WLEDs) are advancing rapidly in replacing the conventional fluorescent and incandescent light sources. However, the current technology of pc-WLEDs limits their large scale indoor lighting applications due to their high correlated color temperature (CCT) and poor color rendering index (CRI). In this work, a single phased full color emitting phosphor in the pyrochlore oxide system, La2Y0.66Sn0.66Sb0.66O7: Bi3+, Eu3+ has been developed by the high temperature ceramic route. The developed phosphors are characterized by powder X-ray diffraction, luminescence and lifetime measurements. Upon near UV excitation wavelength, the singly doped phosphor, La2Y0.66Sn0.66Sb0.66O7: Bi3+ show intense blue green light in the wavelength region 400–600 nm due to the characteristic transitions (3P1 → 1S0) of Bi3+. The emission spectral analysis suggests that there exist two luminescence centers of Bi3+ due to occupation of different crystallographic sites in the pyrochlore lattice of La2Y0.66Sn0.66Sb0.66O7. The deficit of red component in the emission spectra is overcome by the Eu3+ co-doping in the system, La2Y0.66Sn0.66Sb0.66O7: Bi3+, Eu3+ which results in the full color emission covering the visible spectral range up to 700 nm with broad peaks along with sharp narrow characteristic peaks of Eu3+. The full color emission of the La2Y0.66Sn0.66Sb0.66O7: 0.04Bi3+, yEu3+ phosphors can be tuned by adjusting the suitable Eu3+ dopant concentration and using appropriate energy transfer from Bi3+ to Eu3+. The full color emitting phosphor, La2Y0.66Sn0.66Sb0.66O7:0.04Bi3+, 0.06Eu3+ can be realized with the color coordinates (0.30, 0.36), and correlated color temperature (4383K). All these results demonstrate that La2Y0.66Sn0.66Sb0.66O7:xBi3+, yEu3+ are potential single phased full color emitting phosphors for the development of pc-WLEDs.

Substrate dilution and interface structures of tungsten coating deposited by double-glow plasma surface alloying on stainless steel substrate

W-coating layers with varying thicknesses up to 10 μm were deposited by double-glow plasma surface alloying (DGPSA) on finely polished stainless steel (SS304L) substrates to investigate the influence of the substrate on both the W-coating and interface structures. The examination revealed substrate dilution and the presence of oxide crystallites, predominantly FeWO4 and WO2, at the interface between W and SS304L. These observations correlated with the occurrence of cracking and peeling-off of the W-coating. Both Cr and Ni showed decreased distribution in the interface layer compared to their distribution in the W-coating and SS304L substrate. In comparison, Fe demonstrated a more noticeable compositional gradient, decreasing monotonically from SS304L across the interface to the W-coating. The depth distribution of O indicated that its inclusions were influenced not only by DGPSA deposition but also by post-deposition ion-beam milling. Additionally, the presence of spherical particles directly on the substrate's surface provided evidence for surface alloying reactions, while the columnar grains within the interface oxide layer were associated with the texture features of the W-coating, as confirmed by X-ray diffraction and pole-figure measurements. These findings offer valuable insights into the surface alloying process facilitated by DGPSA and its potential for developing W-coatings tailored for plasma-facing applications.

Carboxylate bridging Cd(II)-based 1D coordination polymer: Structure, fabrication of Schottky device and selective sorption of Bromocresol Green

Phenyl-1,3-diacetate (1,3-PDAt) bridging Cd(II)-based 1D coordination polymer {[Cd(1,3-PDAt)(phen)]⋅(MeOH)⋅(H2O)0.5}n, (CP) where 1,10-phenanthroline (phen) serves as chelating ligand has been structurally confirmed by Single Crystal X-Ray Diffraction measurements along with other spectral data. The thermal treatment releases MeOH at ∼90 °C and the final product ends at CdO. The Tauc’s plot evaluates the band gap, 3.87 eV (calculated value, 3.76 eV) using absorption spectral data which marks the semiconducting nature of the material. This has motivated us to fabricate Schottky Diode device and the measured conductance is 8.87 × 10−6 S/m in the dark. Interestingly, 1D CP shows selective and specific sorption of Bromocresol Green (BG) out of four common dyes (Methylene blue, Methyl orange, Rhodamine B, and Bromocresol Green (BG)). Besides, the sorbed BG in the CP is leached out on treating with water and the CP has been re-used for further sorption studies. Thus, the CP is economically recycled which is the first principle of Sustainable Development Goals.

Investigating the effect of Mo doping on structural and ferroelectric properties of BaTiO3 using electron microscopy

The effect of Molybdenum (Mo) doping in pure barium titanate at Ti site has been investigated using electron microscopy, x-ray diffraction and dielectric and impedance spectroscopy. The room temperature XRD data confirms the formation of Mo substituted BaTi0.94Mo0.06O3 in tetragonal symmetry. Even with the minimal doping of Mo, the first two structural transition shifts to the lower temperature by 60 and 30 K, respectively, as compared to pure barium titanate, confirmed via dielectric, polarization and x-ray diffraction measurements. In Mo doped BaTiO3, the cubic to tetragonal phase transition has been observed at ∼335 K, tetragonal to orthorhombic at ∼250 K. The orthorhombic to rhombohedral transition remains almost unaffected with Mo doping. Furthermore, transmission electron microscopy (TEM) has been employed to see the changes in microstructure/domain structure across various ferroelectric phases below 335 K which confirms the emergence of multiple twins in different ferroelectric phases.

Enhanced elastic stability of a topologically disordered crystalline metal-organic framework.

By virtue of their open network structures and low densities, metal-organic frameworks (MOFs) are soft materials that exhibit elastic instabilities at low applied stresses. The conventional strategy for improving elastic stability is to increase the connectivity of the underlying MOF network, which necessarily increases the material density and reduces the porosity. Here we demonstrate an alternative paradigm, whereby elastic stability is enhanced in a MOF with an aperiodic network topology. We use a combination of variable-pressure single-crystal X-ray diffraction measurements and coarse-grained lattice-dynamical calculations to interrogate the high-pressure behaviour of the topologically aperiodic system TRUMOF-1, which we compare against that of its ordered congener MOF-5. We show that the topology of the former quenches the elastic instability responsible for pressure-induced framework collapse in the latter, much as irregularity in the shapes and sizes of stones acts to prevent cooperative mechanical failure in drystone walls. Our results establish aperiodicity as a counter-intuitive design motif in engineering the mechanical properties of framework structures that is relevant to MOFs and larger-scale architectures alike.

Influence of polycarboxylate superplasticizer and polyacrylamide on mirror effect of fair-faced concrete

This work successfully prepared fair-faced concrete with mirror effect. The gray value standard deviation, porosity, crack rate and glossiness of the concrete surface were used to characterize the apparent quality of fair-faced concrete. The effect of polycarboxylate superplasticizer and polyacrylamide viscosity-modifying admixture on mirror effect of fair-faced concrete was investigated. The changes of hydration products and microstructure of fair-faced concrete were monitored by the measurements of X-ray diffraction (XRD), thermogravimetric analysis (TG), scanning electron microscopy (SEM) and mercury intrusion porosity (MIP), and the potential mechanism was analyzed. The results indicate that the polyacrylamide reduces the number and size of Ca(OH)2 and change the morphology of Ca(OH)2 crystals from large-size parallel stacking state to small-size edge corrosion structure. The polyacrylamide can refine the pore size of concrete, the most probable pore size at the optimum dosage is 13.73 nm, which is much lower than that at other dosages. The usage of the polycarboxylate superplasticizer will introduce air, which has adverse effect on the concrete surface. But polycarboxylate superplasticizer can also improve the flowability of concrete and make bubbles easy to discharge. The combined action of polycarboxylate superplasticizer and polyacrylamide contributes the fair-faced concrete for better mirror effect.

Enhancing GaN Nanowires Performance Through Partial Coverage with Oxide Shells.

Core-shell gallium nitride (GaN)-based nanowires offer noteworthy opportunities for innovation in high-frequency opto- and microelectronics. This work delves deeply into the physical properties of crystalline GaN nanowires with aluminum and hafnium oxide shells. Particular attention is paid to partial coverage of nanowires, resulting with exceptional properties. First, the crystal lattice relaxation is observed by X-ray diffraction, photoluminescence, and Raman spectroscopy measurements. A high potential of partial coverage for optoelectronic applications is revealed with photo- and cathodoluminescence spectra along with an exploration of their temperature dependency. Next, the study focuses on understanding the mechanisms behind the observed enhancement of the luminescence efficiency. It is confirmed that nanowires are effectively protected against photoadsorption using partial coatings. This research advances the frontiers of nanotechnology, investigating the benefits of partial coverage, and shedding light on its complex interaction with cores.

Characterization of RF-Sputtered ZnO Thin Film Coatings on Aluminum (Al6061): Microstructure, Wettability, Cavitation, and Corrosion Analysis

The study focuses on the characterization of Aluminum (Al-6061) coated with RF-sputtered Zinc Oxide (ZnO) thin film, aiming to understand the complex interactions between microstructure, wettability, cavitation resistance, and corrosion performance. The study involves the use of various analytical techniques such as Field Emission Scanning Electron Microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and water contact angle (WCA) measurements. The cavitation erosion testing has been conducted under various factors namely jet velocity (m/s), impingement angle (°), and stand-off distance (cm), respectively, and that too at various levels. Further, with the use of RSM, the study also contributes to the interplay in between factors and acquiring optimized results. Moreover, the findings of the study provide valuable insights into the effectiveness of the ZnO coating in enhancing corrosion resistance and reducing mass loss due to cavitation erosion. The study’s results offer significant implications for the engineering and design of protective coatings for Aluminum surfaces, with the potential to enhance durability and performance in various industrial applications.

Synthesis-Dependent Structural and Magnetic Properties of Monodomain Cobalt Ferrite Nanoparticles

This research examines the structural and magnetic properties of monodomain cobalt ferrite nanoparticles with the formula (Co1−xFex)A[Fe2−xCox]BO4. The particles were synthesized using various methods, including coprecipitation (with and without ultrasonic assistance), coprecipitation followed by mechanochemical treatment, microemulsion, and microwave-assisted hydrothermal techniques. The resulting materials were extensively analyzed using X-ray diffraction (XRD) and magnetic measurements to investigate how different synthesis methods affect the structure and cation distribution in nanoscale CoFe2O4. For particles ranging from 15.8 to 19.0 nm in size, the coercivity showed a near-linear increase from 302 Oe to 1195 Oe as particle size increased. Saturation magnetization values fell between 62.6 emu g−1 and 74.3 emu g−1, primarily influenced by the inversion coefficient x (0.58–0.85). XRD analysis revealed that as the larger Co2+ cations migrate from B- to A-sites (decreasing x), the lattice constants and inter-cation hopping distances increase, while the average strength of super-exchange interactions decreases. This study establishes a connection between the magnetic properties of the synthesized samples and their structural features. Importantly, this research demonstrates that careful selection of the synthesis method can be used to control the magnetic properties of these nanoparticles.

Development and experimental validation of a thermo-metallurgical-mechanical model of the laser metal deposition (LMD) process

The current paper presents the development and experimental validation of a thermo-metallurgical-mechanical model for a multi-pass Laser Metal Deposition (LMD) process, with the objective of accurately predicting the resultant constituent phases and residual stresses. The thermal model is calibrated using temperature readings and is shown to accurately capture the transient temperature field and extent of the fusion zone associated with the multi-pass LMD process. The metallurgical model incorporates the kinetics of ongoing solid-state phase transformations (SSPTs) and tempering reactions. The predictions are validated via hardness measurements, demonstrating a very good agreement with the predictions. The developed mechanical model predicts the residual stress field, which is validated using X-ray diffraction measurements, and the comparison also shows a very good agreement between the predictions and measurements. The validated numerical model is then used to explore alternative LMD strategies showing that the choice of deposition strategy can significantly impact resultant constituent phases and residual stresses.