Position Of Diffraction Peak Research Articles

Effect of substrate and Zn doping on the structural, optical and electrical properties of CdS thin films prepared by CBD method

CdS is an important and useful material for photovoltaic applications. In this paper, pure CdS and Zn-doped CdS (CdS:Zn) thin film were fabricated on glass and ITO substrate using chemical bath deposition (CBD) method, to systematically investigate the effect of substrate and Zn concentration on the crystallization behavior, and optical and electrical properties of the CdS thin films by X-ray diffraction, atomic force microscope, X-ray photoelectron spectroscopic, Raman scattering, UV–vis spectrophotometer, and transportation measurement system. The results indicated that no matter what substrate was used, whether glass or ITO substrate, the crystal structure of CdS thin film is always hexagonal phase with (002) as the preferential orientation. And CdS thin film deposited on ITO substrate have a good crystallinity and its morphology is very compact and uniformity. For doping thin films, the results revealed that Zn element has been successfully doped into the lattice of CdS thin film and the position of (002) diffraction peak shifted monotonically from 26.6° to 26.97° with the increase of Zn concentration. Finally, optical and electrical properties were discussed. The optical band gap for the CdS:Zn thin films is bigger than that of the pure CdS thin film, and suitable Zn doping can improve the electrical conductivity of thin film. Our results indicate the CdS:Zn thin films fabricated via CBD method may be more suitable for the application in optoelectronic devices, such as the window layer for cadmium telluride and copper zinc tin sulfide solar cell.

Catalytic growth and characterization of single crystalline Zn doped p-type β-Ga2O3 nanowires

Single crystalline β-Ga2O3 nanowires with different Zn doping contents were grown via catalytic chemical vapor deposition method. The field-emission scanning electron microscopy showed that when the Zn content was 1.3%, the Zn doped β-Ga2O3 nanowires with uniform size and high density were synthesized. The diameter and length of nanowires were about 50 nm and dozens of micron, respectively. The X-ray diffraction measurements indicated that the position of (202) diffraction peak of samples shifted toward lower diffracting angle with increasing Zn content, which was explained by the substitution of Ga3+ by Zn2+ during Zn doping process. Furthermore, the Zn-doped β-Ga2O3 nanowires/n-type β-Ga2O3 thin film p-n homojunction was fabricated. The current-voltage (I-V) characteristic of the homojunction device showed a good rectifying behavior. This result is suggested that the Zn doped β-Ga2O3 nanowires showed p-type conductivity.

Pressure-driven transformation of the ordering in amorphous network-forming materials

The pressure-induced changes to the structure of disordered oxide and chalcogenide network-forming materials are investigated on the length scales associated with the first three peaks in measured diffraction patterns. The density dependence of a given peak position does not yield the network dimensionality, in contrast to metallic glasses where the results indicate a fractal geometry with a local dimensionality of $\ensuremath{\simeq}5/2$. For oxides, a common relation is found between the intermediate-range ordering, as described by the position of the first sharp diffraction peak, and the oxygen-packing fraction, a parameter that plays a key role in driving changes to the coordination number of local motifs. The first sharp diffraction peak can therefore be used to gauge when topological changes are likely to occur, events that transform network structures and their related physical properties.

Determining Individual Phase Flow Properties in a Quench and Partitioning Steel with In Situ High-Energy X-Ray Diffraction and Multiphase Elasto-Plastic Self-Consistent Method

The micromechanical properties of the constituent phases were characterized for advanced high-strength steels (AHSS) produced by a quenching and partitioning (Q&P) process with in situ tensile loading under synchrotron-based, high-energy X-ray diffraction. The constituent phases present are retained austenite and three martensites (tempered, untampered, and freshly formed martensites). For the material investigated, the 200 and 220 lattice strains of the retained austenite phase were calculated by examining the changes of the X-ray diffraction peak positions during deformation. The 200 and 211 lattice strains of the various martensitic phases with similar crystal structures were determined by separating their overlapped diffraction peaks. Apart from tempered and untempered martensite, the diffraction peaks of freshly formed martensite as a result of austenite-to-martensite transformation can also be separated due to a high initial austenite volume fraction. The phase stresses are first estimated with an empirical relationship through the X-ray diffraction elastic constants. A multiphase elasto-plastic self-consistent model is next used for more accurate determination of the constitutive behaviors of the various phases by comparing the predicted lattice strain distributions and global stress–strain curves with the measured ones. The determined constitutive laws will be used for microstructure-based modeling for sheet formability of the Q&P AHSS steel.

Quantification of crystalline fraction of solid slag film using X-ray powder diffraction

This paper introduces a new method to determine the crystalline fraction in samples containing amorphous phases from experimental X-ray diffraction data. Computer generated codes, one for each measured data point, are used to interpret the pattern as to where diffraction peaks exist and what is the angular breadth of each peak's intensity above background. Two parameters are defined that are used to identify the position and intensity of the crystalline phase diffraction peaks. For mold fluxes used in continuous casting, the crystalline fraction of solid slag film is a key factor that can affect heat transfer between solidified shell and mold. In this work, a new method was developed to determine the crystallinity of solid slag films. This method does not require structure parameters or other references, and results can be obtained directly by reading a text file with diffraction data. Results indicate that, there is a positive correlation between crystalline fraction and integrated intensities corresponding to crystalline phases. The selection of integration interval does not have much effect on results. To simplify computations, 20–45°2θwas considered as an appropriate interval.

Synchrotron X-ray microdiffraction of Fe–3 wt%Si steel focusing on sub-boundaries within Goss grains

The microstructure evolved after the initial stage of abnormal grain growth (AGG) in Fe–3wt%Si steel was examined using synchrotron X-ray microdiffraction to identify the sub-boundaries, which had been suggested to induce the selective AGG of Goss-oriented grains. The splitting of Laue diffraction peaks caused by sub-boundaries was observed only in Goss grains and not in matrix grains in the entire samples. The sub-boundaries were measured to have very low misorientation angles in the range of 0.1–0.6°. The characteristics and morphologies of sub-boundaries in Goss grains were analyzed based on the splitting directions and positions of Laue diffraction peaks.

General 2.5 power law of metallic glasses

Metallic glass (MG) is an important new category of materials, but very few rigorous laws are currently known for defining its "disordered" structure. Recently we found that under compression, the volume (V) of an MG changes precisely to the 2.5 power of its principal diffraction peak position (1/q1). In the present study, we find that this 2.5 power law holds even through the first-order polyamorphic transition of a Ce68Al10Cu20Co2 MG. This transition is, in effect, the equivalent of a continuous "composition" change of 4f-localized "big Ce" to 4f-itinerant "small Ce," indicating the 2.5 power law is general for tuning with composition. The exactness and universality imply that the 2.5 power law may be a general rule defining the structure of MGs.

A Study of Stacking Faults and Superlattice Ordering in Some Li-Rich Layered Transition Metal Oxide Positive Electrode Materials

Li-rich layered transition metal oxides such as Li[Li0.2Ni0.2Mn0.6]O2 have in-plane ordering between the excess Li atoms and the transition metal (TM) atoms in the transition metal layer. The √3a × √3a superlattice in the TM layer causes superlattice Bragg peaks in their X-ray diffraction patterns. This article describes the relation between the metal composition of the materials, stacking faults and superlattice ordering. The XRD patterns were fitted with a program called FAULTS, which treats the effect of stacking faults on the superlattice peak shapes. The superlattice peak positions of Li[Li1/3-2x/3NixMn2/3-x/3]O2 materials changed monotonically with Ni content (x), as did the positions of the main diffraction peaks of the base structure. This proves that the superlatices peaks originate from the Li[Li1/3-2x/3NixMn2/3-x/3]O2 solid solution and are not caused by any domains of second phase such as Li2MnO3. Fitting the XRD patterns with FAULTS revealed that the stacking fault probability increased monotonically with Ni content.

Ordering of protein and water molecules at their interfaces with chitin nano-crystals.

Synchrotron X-ray diffraction was applied to study the structure of biogenic α-chitin crystals composing the tendon of the spider Cupiennius salei. Measurements were carried out on pristine chitin crystals stabilized by proteins and water, as well as after their deproteinization and dehydration. We found substantial shifts (up to Δq/q=9% in the wave vector in q-space) in the (020) diffraction peak position between intact and purified chitin samples. However, chitin lattice parameters extracted from the set of reflections (hkl), which did not contain the (020)-reflection, showed no systematic variation between the pristine and the processed samples. The observed shifts in the (020) peak position are discussed in terms of the ordering-induced modulation of the protein and water electron density near the surface of the ultra-thin chitin fibrils due to strong protein/chitin and water/chitin interactions. The extracted modulation periods can be used as a quantitative parameter characterizing the interaction length.

Hydrothermal synthesis of MoS2 nanosheets films: Microstructure and formation mechanism research

MoS2 nanosheets films were successfully prepared by Ti foil assisted hydrothermal synthesis method (labeled as Ti-MoS2 nanosheets films). The downside and upside of the films showed different novel morphologies with nanosheets arranged regularly and flowerlike microspheres, respectively. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM). X-ray diffraction patterns showed that the peaks along (002) planes made a wide shift from 14.2° to 9.4° compared to its standard position located at 14.2° at the beginning of the hydrothermal process, then gradually returned back to its normal position with the hydrothermal treatment time going on. However, time was not the only element to influence the position of the main diffraction peaks, a relatively low hydrothermal treatment temperature could also lead to the diffraction peaks' shift. In addition, TEM images indicated that the nanosheets film with hydrothermal treatment time for 24h had a good single-crystal structure. Otherwise, the formation mechanism was carefully discussed and a possible formation mechanism was proposed.

Microstructure, optical and structural characterization of Cd0.98Fe0.02S thin films co-doped with Zn by chemical bath deposition method

Fe-doped CdS (Cd0.98Fe0.02S) and Fe, Zn co-doped CdS (Cd0.98−xZnxFe0.02S (x=0.02, 0.04, and 0.06)) thin films have been successfully deposited on glass substrate by chemical bath deposition technique using aqueous ammonia solution at pH = 9.5. Phase purity of the samples having cubic structure with (111) as the preferential orientation was confirmed by X-ray diffraction technique. Shift of X-ray diffraction peak position towards higher angle side and decrease of lattice parameters, volume and crystallite size confirmed the proper incorporation of Zn into Cd–Fe–S except Zn=6%. The compositional analysis (EDX) showed that Cd, Fe, Zn and S are present in the films. The enhanced band gap and higher transmittance observed in Cd0.94Zn0.04Fe0.02S films are the effective way to use solar energy and enhance its photocatalytic activity under visible light. The enhanced green band emission than blue band by Zn-doping evidenced the existence of higher defect states.

Study of Raman Spectroscopy on Graphene Phase from Heat Treatment of Coconut (<i>Cocus nucifera</i>) Shell

Coconut (Cocus Nucifera) shell as the main ingredient in this research has been heat-treated at temperature of 1000°C in atmospheric condition aiming to obtain the expected phase of graphene. After heat treatment, an additional special treatment was given, where sample was then rinsed with distilled water. Furthermore, the heated coconut shell was characterized by Raman Spectroscopy (785 nm) and X-ray diffractometry. Based on the treatment and characterization conducted, all samples were likely to contain reduced graphene oxide (RGO) phase.The XRD data have supported the existence of RGO with the diffraction peak position (2q) at 25o and 45o. Evidence is also given by the result of Raman Spectroscopy which produces peaks (denoted by D and G bands) located at wave numbers of 1300 cm-1 and 1590 cm-1. The value of the ratio ID/IG of the two samples in the figures are 2.6 and 2.51 (matched with ratio ID/IG of RGO). The ID/IG ratio of sample which was rinsed by distilled water is higher that those without rinsing treatment.

Origin of melting point depression for rare gas solids confined in carbon pores.

To obtain insights into the mechanism of the melting-point depression of rare gas solids confined in crystalline carbon pores, we examined the freezing and melting behavior of Xe and Ar confined to the crystalline pores of ordered mesoporous carbons as well as compressed exfoliated graphite compared to the amorphous pores of ordered mesoporous silicas, by means of X-ray diffraction. For the Xe and Ar confined to the crystalline carbon pores, there was no appreciable thermal hysteresis between freezing and melting. Furthermore, the position of the main diffraction peak did not change appreciably on freezing and melting. This strongly suggests that the liquids confined in the carbon pores form a multilayered structure parallel to the smooth walls. For the Xe and Ar confined to the amorphous silica pores, on the other hand, the position of the main diffraction peak shifted into higher scattering angle on freezing suggested that the density of the confined solid is distinctly larger than for the confined liquid. Using compressed exfoliated graphite with carbon walls of higher crystallinity, we observed that three-dimensional (3D) microcrystals of Xe confined in the slit-shaped pores melted to leave the unmelted bilayers on the pore walls below the bulk triple point. The lattice spacing of the 3D microcrystals confined is larger by ∼0.7% than that of the bilayer next to the pore walls in the vicinity of the melting point.

In Operando Strain Measurement of Bicontinuous Silicon‐Coated Nickel Inverse Opal Anodes for Li‐Ion Batteries

Elastic strains are measured in operando in a nanostructured silicon‐coated nickel inverse opal scaffold anode, using X‐ray diffraction to study the Si (de)lithiation‐induced Ni strains. The volume expansion upon lithiation of the Si in the anode is constrained by the surrounding Ni scaffold, causing mismatch stresses and strains in the Si and Ni phases during cycling. The Ni strains are measured in operando during (dis)charge cycles, using diffraction peak position and peak broadness to describe the distribution of strain in the Ni. During lithiation, compressive strains in the Ni first increase linearly with charge, after which a gradually decreasing strain rate is observed as the maximum lithiation state is approached; upon delithiation a similar process occurs. In‐plane average compressive strains on the order of 990 ± 40 με are measured in the Ni scaffold during lithiation, corresponding to compressive stresses of 215 ± 9 MPa. The decreasing strain rates and decreasing maximum and recovered strains suggest that plasticity in Ni and/or Si, as well as delamination between Ni and Si, may occur during cycling. Rate sensitivity in capacity is correlated with strain and a maximum Ni compressive stress of 230 ± 40 MPa is measured at the maximum state of lithiation.

Structure and Properties of Sol Gel Fabricated Na0.5Nd0.5Bi4Ti4O15 Ceramics

Na0.5Nd0.5Bi4Ti4O15 (NNBT) and pure SrBi4Ti4O15 (SBT) ceramics are prepared by sol gel method based on pechini process and their results are compared. Lowering of the sintering temperature and densification of the ceramics are obtained by making use of this fabrication method. The positions of the X-ray diffraction peaks are in good agreement with that of standard orthorhombic pattern. There is a decrease in the lattice parameter values and increase in the orthorhombicity with double ion doping suggesting strong structural distortion with the substitution of lower ionic radii ions. The microstructural features analyzed through Scanning electron microscopy show grains in the form of platelets. Measurements of dielectric, ferroelectric and electromechanical properties are conducted. The incorporation of smaller Na and Nd in Sr site increased Curie temperature from 823K to 923K, decreased dielectric constant at Curie temperature from 2336 to 737 and also decreased room temperature dielectric loss from 0.051 to 0.024 measured at 10kHz frequency. There is a decrease in 2Pr value from 19.6μC/cm2 to 2.8μC/cm2 and coercive field value from 85.3kV/cm to 45.2kV/cm with doping showing doping affect on the polarization phenomenon. The electromechanical coupling factor values (kt and keff) for pure sample are 0.47 and 0.44 respectively while for doped sample are 0.76 and 0.72 respectively. High electromechanical coupling factor values show that piezoelectric properties are greatly improved by such substitution. Impedance analysis indicates that the conduction in the present samples occurs through grain and grain boundaries. Results are correlated with defect structure caused by doping. Low dielectric loss, high Curie temperature and high coupling factor values make these materials promising piezoelectric materials for high-temperature applications.

Mg Substitution Clarifies the Reaction Mechanism of Olivine LiFePO4

Understanding the reaction mechanism of olivine compounds as electrode materials for lithium lithium‐ion batteries have has received much attention recently. The question whether olivine LiFePO4 undergoes two‐phase or non‐nonequilibrium single‐phase reaction during electrochemical processes has taken center stage in the understanding of the faster reaction kinetics observed in this material. Here, the lithiation/delithiation mechanism of Mg Mg‐substituted LiFePO4 using high high‐resolution X‐ray diffraction(XRD), transmission electron microscopy(TEM), and electrochemical measurements is reported. Ex situ partially (de)lithiated olivine‐ LiMg0.2Fe0.8PO4 show the existence of stable equilibrium intermediate phases as characterized by the presence of more than two phases and broadness of diffraction peaks. Electron energy loss spectroscopy profiles across individual nanoparticles further confirm uniform lithiation with a constant Fe–L3 energy measured across each nanoparticle, suggestive of solid solution behavior in individual particles. In addition, a continuous shift in the diffraction peak position is observed even in the “two‐phase” region in the ex situ electrochemical (de)lithiated electrodes.

Lithium silicide nanocrystals: synthesis, chemical stability, thermal stability, and carbon encapsulation.

Lithium silicide (LixSi) is the lithiated form of silicon, one of the most promising anode materials for the next generation of lithium-ion batteries (LIBs). In contrast to silicon, LixSi has not been well studied. Herein we report a facile high-energy ball-milling-based synthesis of four phase-pure LixSi (x = 4.4, 3.75, 3.25, and 2.33), using hexane as the lubricant. Surprisingly, the obtained Li3.75Si phase shows significant downward shifts in all X-ray diffraction peak positions, compared with the standard. Our interpretation is that the high-energy ball-mill-synthesized Li3.75Si presents smaller internal pressures and larger lattice constants. The chemical-stability study reveals that only surface reactions occur after Li4.4Si and Li3.75Si are immersed in several battery-assembly-related chemicals. The thermal-stability study shows that Li4.4Si is stable up to 350 °C and Li3.75Si is stable up to 200 °C. This remarkable thermal stability of Li3.75Si is in stark contrast to the long-observed metastability for electrochemically synthesized Li3.75Si. The carbon encapsulation of Li4.4Si has also been studied for its potential applications in LIBs.

Structural modifications of swift-ion-bombarded metallic glasses studied by high-energy X-ray synchrotron radiation

Modifications of structural arrangements including relaxation processes were investigated in swift-heavy-ion-bombarded Fe73Cu1Nb3Si16B7 metallic glass. The irradiation of as-quenched amorphous ribbons was accomplished with 3MeVu−1 (u is atomic mass unit) and 11.1MeVu−1 Au ions with total fluences of up to 1×1013 ions cm−2. Specimens irradiated with 3MeVu−1 ions were subsequently annealed for 4h at 350°C. Ion-irradiated samples including those heat-treated were studied using in situ temperature-dependent diffraction of high-energy X-ray synchrotron radiation (wavelength of 0.020689nm). Cyclic heating–cooling regimes were applied during the measurements. A tendency towards a higher degree of disorder was revealed as a function of the ion fluence in both types of alloys. During the first heating–cooling cycle, a remarkable hysteresis is observed in the position and line width of the first diffraction peak, especially in the as-quenched irradiated alloys. The hysteresis increases with rising ion fluence but vanishes completely after the first heating–cooling cycle. No hysteresis is found in the irradiated and subsequently annealed alloys. The irradiation-induced structural modifications have some features similar to the effects caused by mechanical deformation.

Macroscopic and microscopic strain of SiO2 glass under uniaxial compression

Although SiO2 glass is brittle due to its covalency and the lack of dislocation movement seen in crystals, it can deform without fracturing when compressed to high pressures. The phenomenon may be attributable to the well-known permanent densification by the reconstruction of the network structure consisting of SiO4 tetrahedra. To explore so-called plastic deformation without permanent densification, we measured the change in size (macroscopic strain) of uniaxially-compressed disk-shaped SiO2 glass by an optical microscope [1]. Also, to understand the anisotropy in structure (microscopic strain), we measured the azimuth-angle dependence of the position of the first sharp diffraction peak (FSDP) of uniaxially-compressed SiO2 glass with a radial X-ray diffraction technique [2]. In the microscope observation, the glass was found to deform largely without fracturing up to at least 20 GPa from 6-8 GPa, where uniaxial conditions were achieved. In the X-ray diffraction observation, a large anisotropy was found in the FSDP which corresponds to the intermediate-range network structure of the glass. The recovered glass was examined by the radial X-ray diffraction up to a high-Q range and was found to remain largely anisotropic (equivalent to about 2 GPa in differential stress) in the intermediate-range network structure and not to remain anisotropic in the short-range SiO4 tetrahedral structure. It seems intuitive that the residual anisotropy is due to the anisotropic reconstruction of the network structure during permanent densification. However, the macroscopic strain measured in the microscope observation was an order of magnitude larger than the microscopic strain in the X-ray diffraction observation, and therefore it cannot be explained solely by the anisotropic permanent densification. The permanent densification may also enhance the reconstruction of the network structure and therefore plastic deformation.

Effect of Compressing Deformation on the Crystal Structure of Stress-Induced Martensitic in Ti-10V-2Fe-3Al Titanium Alloy

Abstract The regular and obvious change in the diffraction peak position of certain crystal planes of stress-induced martensite at different compression deformation degrees and the orientation evolution of stress-induced martensite crystal plane for Ti-10V-2Fe-3Al titanium alloy were studied. The results show that the lattice parameters are not constant in compressing. The a axis of the unit cell shrinks and the b increases while the c fluctuates. This is attributed to the great change in the diffraction peak positions of stress-induced martensite. Orientational changes are observed in stress-induced α″ phase during compressing. (020) and (021) crystal plane are inclined to be preferred orientation during compressing.