General Structure Analysis System Research Articles

Principal Preferred Orientation Evaluation of Steel Materials Using Time-of-Flight Neutron Diffraction

Comprehensive information on in situ microstructural and crystallographic changes during the preparation/manufacturing processes of various materials is highly necessary to precisely control the microstructural morphology and the preferred orientation (or texture) characteristics for achieving an excellent strength–ductility–toughness balance in advanced engineering materials. In this study, in situ isothermal annealing experiments with cold-rolled 17Ni-0.2C (mass%) martensitic steel sheets were carried out by using the TAKUMI and ENGIN-X time-of-flight neutron diffractometers. The inverse pole figures based on full-profile refinement were extracted to roughly evaluate the preferred orientation features along three principal sample directions of the investigated steel sheets, using the General Structure Analysis System (GSAS) software with built-in generalized spherical harmonic functions. The consistent rolling direction (RD) inverse pole figures from TAKUMI and ENGIN-X confirmed that the time-of-flight neutron diffraction has high repeatability and statistical reliability, revealing that the principal preferred orientation evaluation of steel materials can be realized through 90° TD ➜ ND (transverse direction ➜ normal direction) rotation of the investigated specimen on the sample stage during two neutron diffraction experiments. Moreover, these RD, TD, and ND inverse pole figures before and after the in situ experiments were compared with the corresponding inverse pole figures recalculated from the MUSASI-L complete pole figure measurement and the HIPPO in situ microstructure evaluation, respectively. The similar orientation distribution characteristics suggested that the principal preferred orientation evaluation method can be applied to the in situ microstructural evolution of bulk orthorhombic materials and spatially resolved principal preferred orientation mappings of large engineering structure parts.

Mn2+ doped LiBaF3 fluoride perovskite single crystal with broadband infrared luminescence pumped by blue LED

In this study, Mn2+ ions doped lithium barium fluoride single crystals (LiBaF3: Mn2+) with perovskite structure were successfully prepared by a reformative Bridgman technique. A near-infrared (NIR) emitting broadband of the single crystal with a peak wavelength of 767 nm and a full width half maxima (FWHM) of 77 nm is owing to the 4T1g(4G)→6A1g(6S) transition of the Mn2+ ions in strong crystal field. Mn2+ ions replace the lattices of Li+ ions from the results of Rietveld structure refinements of the crystals performed by General Structure Analysis System (GSAS) program. A high internal quantum efficiency (41.4%) can be obtained in the synthesized single crystal upon excitation of 494 nm, and the emission intensity of this single crystal at 473 K remains at 42.9% of that at 298 K. Therefore, the LiBaF3: Mn2+ single crystal is a promising candidate for NIR solid-state light-emitting material due to its effective broadband NIR emission. This work offers a novel route to rational design of efficient broadband NIR luminescence and provides a new insight into Mn2+ luminescence and its applications.

Structural and Electrochemical Analysis of SmBa0.8Sr0.2Co2O5+δ Cathode Oxide for IT-SOFCs

The double perovskite SmBa0.8Sr0.2Co2O5+δ(SBSC82)wasprepared using a conventional techniqueand evaluatedas solid oxide fuel cells (SOFCs) cathode materialwhich operatesat intermediate temperatures. The SBSC82 cathode powder was produced using the solid-state reaction technique and an alumina ball as a grinder. XRD was used to determine the cathode powder structure, and the microstructure was analyzed using SEM.The oxygen content (δ) for the SBSC82 cathode was recorded by a thermogravimetric analyzer.Powder patterns and lattice parameters weredetected using General Structure Analysis System (GSAS) software. The symmetrical cell was examined using a Voltalab PGZ 301 potentiostat. The δ of SBSC82 cathode reached5.68, 5.43, and 5.22 at 400oC, 600oC, and 800oC.It was found that SBSC82 oxide showasa simple perovskite-type structure with tetragonal P4/mmm.The polarization resistance (Rp) of the symmetrical cell with SDC|SBCS82|SDC configuration reached of 0.420Ω.cm2, 0.091 Ω.cm2,and 0.041 Ω.cm2at 650oC, 750oC, and 850oC, respectively.Single cell specimen achieves a power density of 377 mW/cm2under humidified air/hydrogen.

Study of the changes in the structure and optical properties of MgxCo1-xCr2-yAlyO4 spinel caused by A/B site ion substitution

In this work, nanosubmicron blue-green pigment powder based on the composition of MgxCo1-xCr2-yAlyO4（0 = x ≤ 1, 0 = y ≤ 2）was prepared by a gel casting method. X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Rietveld refinement with GSAS (General Structure Analysis System), and UV–Vis absorption spectroscopy were used to study the phase composition, grain size, morphology, cation distribution in the crystal structure and spectral absorption of the samples. Colour parameters were also studied by using a colour measurement spectrophotometer. The studies demonstrate that the distribution of cations in the crystal structure is disordered and that divalent and trivalent cations are mixed to occupy tetrahedral and octahedral sites. Furthermore, the substitution of ions at the A/B site leads to a change in the cation distribution ratio at the tetrahedral and octahedral sites. With increasing Mg2+ doping concentration, the inversion parameter of the spinel increases, while with increasing Al3+ doping concentration, the inversion parameter of the spinel decreases. In addition, changes in the calcining atmosphere lead to a change in the oxygen vacancy content in the structure. Under the condition of a reductive atmosphere, the oxygen vacancy content significantly increases, and the inversion parameter also increases. The colour difference for the synthesized MgxCo1-xCr2-yAlyO4 spinel powder is related to the proportion of chromophore ions occupying tetrahedral and octahedral sites and the number of oxygen vacancies.

Strength of tantalum to 276 GPa determined by two x-ray diffraction techniques using diamond anvil cells

Tantalum (Ta) is a metal that has useful properties that make it useful in extreme environments. It is, therefore, important to understand how Ta performs in such extreme conditions by accurately measuring its properties. In this work, the yield strength of tantalum has been measured at pressures up to 276 GPa using axial and radial x-ray diffraction (XRD) methods in diamond anvil cells (DACs). We measured strength using XRD in a radial DAC to 50 GPa, in an axial DAC to 60 GPa using diamonds with standard flat culets, and in a final experiment to 276 GPa using toroidal diamond anvils. The radial XRD data were refined using the Material Analysis Using Diffraction Rietveld software package to extract lattice strain and the yield strength. The axial data were refined using the General Structure Analysis System II and a linewidth method was used to calculate the yield strength. The yield strength measured near ambient pressure was found to be 0.5 GPa and increased with a pressure of up to 50 GPa, where the yield strength plateaued at a value of 2.4 GPa. At pressures above 60 GPa, the strength increased again to a maximum value of 9 GPa at the highest pressure of 276 GPa. The data from the three experiments show good agreement between the methods and previously reported experimental data. This agreement illustrates the value of axial diffraction data for material strength determination and allows for measurements at multi-hundreds of GPa using toroidal DACs.

Assessing Rietveld refinement results on silicon carbide nanoparticles produced by magnesiothermal treatment

Collection and evaluation of X-ray diffraction (XRD) data are essential not purely for phase and structural investigation, but more importantly for all intends and purposes of comprehensive materials characterizations. Incorrect XRD analysis result will lead to misinterpretation of the phase and structural characteristics. The worst part is that instigates inappropriate interpretation of other phase-dependent or structural-dependent properties, e.g. electric, magnetic, or thermodynamic properties. Consequently, accurate phase identification and crystal structure quantification from XRD data is inevitable prior to further materials characterizations, most significantly for nanomaterials. In this present study, we reported the complete XRD qualitative and quantitative analyses of silicon carbide (SiC) nanoparticles. The phase identification was run using X’Pert High Score Plus (HSP) software. Furthermore, the crystal structure computation was executed by means of different Rietveld-based computer programs, i.e. HSP, MAUD (Material Analysis using Diffraction), GSAS (General Structure Analysis System) and Rietica. Our research revealed that the synthesized silicon carbide preserved a cubic crystal structure. MAUD and GSAS could predict the equivalent particle size which was close to that of captured by transmission electron microscopy (TEM). In addition, MAUD produced the most accurate value of the particle size. In this case, Rietica and MAUD extracted similar lattice parameter of the silicon carbide. At last but not least, the electron density mapping also presented to confirm the cubic crystal structure formation of the silicon carbide nanoparticles.

Strong red emission with excellent thermal stability in double-perovskite type Ba2GdSbO6:Eu3+ phosphors for potential field-emission displays

Abstract The novel strong red-emitting in double-perovskite type Ba2GdSbO6:Eu3+ phosphors was successfully demonstrated by the simple high-temperature solid-state reaction at 1400 °C. The crystal structure was investigated by the X-ray diffraction analysis and further studied via employing the General Structure Analysis System. The chemical purity, surface crystalline function, elemental mapping, energy dispersive X-ray spectroscopy and photoluminescence behaviors were analyzed in detail. The decay curve of the optimized sample was measured with the long lifetime value of 3.51 ms and its microenvironment among doping ions was further investigated by the Judd-Oflet theory. Furthermore, the thermal stability was evaluated, and its emission intensity still remained 79.27% at 483 K. Eventually, the cathodoluminescence (CL) emission spectra exhibited strong emission intensity under low accelerating voltages, suggesting that the red-emitting Ba2GdSbO6:Eu3+ phosphors with excellent thermal stability and strong CL emission intensity could be considered as a promising red-emitting material for field-emission displays.

The effects of additives in to heat treatment temperature and time on the crystallinity of lithium silicate glass-ceramic

The glass powders were prepared from binary system of 45 wt.% Li2O and 55 wt.% SiO2 and melted in platinum crucible (90% Pt- 10% Rh) at 1195 °C for 1:15 hr. The glass molten was rapid cooled in cold water at 3°C and the produced frit was milled in agate mortar and four sample groups were prepared. In the first group the temperature changes of heat treatment 750, 800, 850, 900 and 950°C was studied. Second group the time changes of heat treatment 2, 4, 6, 8 and 10 hr. was examined. Third group the addition effect of P2O5 4, 7, 11, 14 and 18 wt.% as nucleating agent was studied. Fourth group the addition changes of nucleating agent mixing P2O5 and TiO2 (quarter of P2O5 percentages as same above) was inspected. XRD, AFM and optical microscope had been done for all four group specimens. Crystalline phase percentages were calculated from XRD histogram by GSAS (General Structure Analysis System) and EXPGUI. The grain size distribution and average diameter of the crystalline phases for all four group specimens were calculated by AFM measurement. The density and mass fraction of crystalline phases were calculated by optical microscope image analyses by image J 1.52i. The results indicated good crystalline phase percentages, phases density, mass fraction and average diameter on nano-scale for 4 wt.% of (3 wt.% P2O5- 1 wt.% TiO2), heat treated at temperature 950°C for 6 hrs.

Rietveld refinement of Sm0.55Sr0.45Mn0.4Fe0.6O3

Single crystals of Sm0.55Sr0.45Mn0.4Fe0.6O3were grown by an optical floating zone technique in an oxygen atmosphere. The powder X-ray diffraction pattern for the grown crystal revealed single-crystalline nature. The lattice parameters and atomic structure were refined and indexed using a General Structure Analysis System (GSAS) to an orthorhombic structure with lattice parametersa= 5.4415 (32) Å,b= 7.6994 (27) Å,c= 5.43868 (28) Å, and space group Pnma.

Luminescence properties of PbF2:Nd3+,Er3+, Yb3+Phosphors and it’s multi-wavelength sensitive bidirectional conversion mechanism

In this paper, PbF2:Nd3+, Er3+, Yb3+ bidirectional conversion phosphors were successfully prepared by high temperature solid-state method, and characterized by X-ray powder diffraction (XRD), general structure analysis system structure refinement, photoluminescence spectra and lifetime analysis methods. X-ray diffraction and refinement results analyzed phase composition and changes in cell parameters. Intense characteristic emissions of the samples were observed when excited under ultraviolet (378 nm) and different infrared wavelengths (808 nm, 980 nm). Under 808 nm excitation, the PbF2:3mol%Nd3+, 1.5mol%Er3+, 13.5mol% Yb3+ phosphors reached the maximum emission intensity among all samples. In order to study the effect of the Nd3+ ion on the luminescence mechanism, the decay curves of the Er3+: 4S3/2 level at 550 nm under pulsed 808 nm and 980 nm excitation were analyzed. Finally, the down-conversion and up-conversion multi-wavelength sensitive luminescence mechanisms were discussed.

Influences of sputtering power and annealing temperature on the structural and optical properties of Al2O3:CuO thin films fabricated by radio frequency magnetron sputtering technique

In the present study, we report the high visible to near infrared (NIR) transparent Al2O3:CuO thin films prepared using homemade high purity sputtering target by radio frequency magnetron sputtering technique with sputtering powers of 100, 200 and 300 W at room temperature and the prepared films were annealed at 300, 600 and 1000 °C for 1 h. X-ray diffraction analysis confirmed the amorphous formation of the deposited films. The obtained X-ray profiles of the sputtering target are refined using Rietveld refinement technique through the program package of general structure analysis system with EXPGUI interface. Optical study showed the sputtering power and annealing temperature persuaded red shift in absorption edge and as a consequence the shrinkage in optical band gap was observed. The obtained high average transparency of 87–96% in the wavelength range 400–1100 nm validates the transmittance of as-deposited and annealed Al2O3:CuO thin films is well extended into the near infrared region. The obtained optical transmittance and absorbance data were utilized to calculate various optical parameters.

Materials for learning use of GSAS-II

The General Structure Analysis System (GSAS-II) package provides materials and crystallographic analysis for all types of diffraction data. It was initially made available with very limited capabilities, but over much of the last decade the features have been expanded, so that GSAS-II is now a comprehensive tool for nearly all types of structural and materials characterization studies. The need to provide materials to teach use of GSAS-II, while the software has been undergoing constant revision and expansion, has required new approaches for documentation. This has included providing tutorials, as each major new capability has been added, and context-sensitive help for each section of the program. Comments in the code are also expanded into a software reference guide. Most recently, video versions of more than half of the tutorials were created and others were provided with animated graphics. All GSAS-II documentation is web-based.

Protein refinement with GSAS-II

The General Structure Analysis System (GSAS)-II software package is a fully developed, open source, crystallographic data analysis system written almost entirely in Python. For powder diffraction, it encompasses the entire data analysis process beginning with 2-dimensonal image integration, peak selection, fitting and indexing, followed by intensity extraction, structure solution and ultimately Rietveld refinement, all driven by an intuitive graphical interface. Significant functionality of GSAS-II also can be scripted to allow it to be integrated into workflows or other software. For protein studies, it includes restraints on bond distances, angles, torsions, chiral volumes and coupled torsions (e.g. Ramachandran Φ/Ψ angles) each with graphical displays allowing visual validation. Each amino acid residue (and any ligands) can be represented by flexible rigid bodies with refinable internal torsions and optionally fully described TLS thermal motion. The least-squares algorithm invokes a Levenberg-Marquart minimization of a normalized double precision full matrix via Singular Value Decomposition providing fast convergence and high stability even for a large number of parameters. This paper will focus on the description of the flexible rigid body model of the protein and the details of the refinement algorithm.

Crystal Structure Analysis of Electromagnetic Wave Absorber Material BaFe12-xTix/2Znx/2O19Based

The optimization of BaFe12-xTix/2Znx/2O19 (x=2.2; 2.4; 2.6; 2.8)single phase composition have been performed. The materials were synthesized by solid state reaction method through mechanical milling technique.The materials were made from the mixture of oxide materials, which are BaCO3, Fe2O3, TiO2 and ZnO. The mixture was milled for five hours using a High Energy Milling (HEM), was dried at 100°C in the Oven and then was sintered at 1000°C for five hours in the Furnace. The phase identification of BaFe12-xTix/2Znx/2O19 (x=2.2; 2.4; 2.6; 2.8) were carried out by using a Match Program while the crystal structure analysis were investigated by using a General Structure Analysis System (GSAS) program. The refinement results of x-ray diffraction pattern showed that the sample of x ≤ 2.4 have a BaFe12O19 single phase while the sample of x> 2.4 have two phases, which are BaFe12O19 and ZnFe2O4 phases. The surface morphology of sample and the element of sample were identified through an analysis of Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS) data.

Tunable luminescence and energy transfer properties in YVO4:Bi3+,Ln3+ (Ln = Dy, Sm, Eu) phosphors prepared by microwave sintering method

YVO4:Bi3+,Ln3+ (Ln = Dy, Sm, Eu) phosphors were successful synthesized by microwave sintering method, and characterized by X-ray powder diffraction, scanning electron microscope, photoluminescence spectra, lifetime, quantum efficiency and general structure analysis system structure refinement. Refinement results indicated that the introduced ions occupy the sites of Y3+. Under 275 nm excitation, the luminescent intensity of YVO4:Bi3+ samples reach the maximum when Bi3+ concentration is 0.02, the broad excitation spectrum of YVO4:Bi3+ has a strongest peak at near 343 nm. Doped Bi3+ can effectively improve the emission intensity of YVO4:Ln3+. The energy transfer mechanism of Bi3+ → Ln3+ was dipole-quadrupole mechanism of electric multipole interaction. The critical distance (Rc) between Ln3+ and Bi3+ were calculated by concentration quenching method. Emitting color of YVO4:Bi3+,Ln3+ phosphors were tunable by adjusting Ln3+ content. In a word, the material has a good application prospects on light emitting diodes.

Stochastic and Deterministic Crystal Structure Solution Methods in GSAS-II: Monte Carlo/Simulated Annealing Versus Charge Flipping

Crystallographic studies frequently involve the determination of a previously unknown crystal structure; General Structure Analysis System (GSAS)-II provides two methods for this purpose. The Monte Carlo/simulated annealing method is fundamentally stochastic in nature; random trials are tested for suitability by comparing calculated structure factors with a suite of observed ones. In contrast, the charge flipping method may begin with a suite of random structure factor phases, but the subsequent mathematical steps are entirely deterministic even though they appear to display chaotic behavior. This paper will briefly describe these methods as implemented in GSAS-II, illustrating their use with examples.

Modification of Pseudobrookite Fe2-XMnxTiO5 with Solid State Reaction Method using a Mechanical Milling

Modification of pseudobrookite Fe2-xMnxTiO5 with solid state reaction method using a mechanical milling has been synthesized. Raw materials used to prepare these samples were Fe2O3, MnCO3, and TiO2. Fe2O3 and TiO2 powders (ratio of 1:1) were mixed with MnCO3 powder at various composition of x = 0; 0.1; 0.2; 0.3; 0.4; 0.5; and 1, which each composition was added with 50 ml ethanol and then milled for 5 hours through high energy milling, after that sintered at 1000 °C for 5 hours by using box furnace. The phases of Fe2-xMnxTiO5 were measured by using X-ray diffraction (XRD) and then identified by using Match program. The crystal structure was analyzed by using the program of General Structure Analysis System (GSAS). Quality fitting of Rwp and χ2 (chi-squared) are relatively good because based on the curve of normalized error distribution looks just left background and its normal probability plot shows the value of comparable between observation and expectation. The refinement analyses of X-ray diffraction patterns showed that the samples formed single phase for x ≤ 0.3. However, the samples of x > 0.3 were multi-phases. The single phase of sample had composition of pseudobrookite Fe2TiO5 with orthorhombic structure, space group of C m c m (63), the lattice parameters of a = 3.7390 Å, b = 9.7790 Å, and c = 9.9780 Å, α = β = γ = 90°, V = 364.83 Å3, and ρ = 4.360 g.cm-3. Meanwhile, the other phase analysis for the composition of x > 0.3 is bixbyite (FeMnO3). The bixbyite has a cubic structure, under the space group of I a - 3 (206), the lattice parameters of a = b = c = 9.40 Å, α = β = γ = 90°, V = 830.58 Å3, and ρ = 5.078 g.cm-3.

The Phase Transformation and Crystal Structure Studies of Strontium Substituted Barium Monoferrite

Unlike other AFe2O4 ferrite materials, Barium Monoferrite (BaFe2O4) have an orthorhombic structure which is very interesting to further study the crystal structure and phase formation. In this study, Strontium substituted Barium Monoferrite in the form of Ba(1-x)Sr(x)Fe2O4 has successfully been synthesized through solid state reaction method which includes BaCO3, SrCO3, and Fe2O3 as starting materials. Ba(1-x)Sr(x)Fe2O4 was made by varying the dopant composition of Strontium (Sr2+) from x = 0, 0.1, 0.3, and 0.5. Each composition was assisted by ethanol and continued to the milling process for 5 hours then followed by sintering process at 900 °C for 5 hours. The phase transformation was studied by using X-ray diffractometer (XRD) and Rietveld refinement using General Structure Analysis System (GSAS) also 3D crystal visualization using VESTA. Referring to the refinement results, a single phase of BaFe2O4 was formed in x = 0 and 0.1. The composition has orthorhombic structure, space group B b21m, and lattice parameters of a = 19.0229, b = 5.3814 c = 8.4524 Å, α = β = γ = 90° and a = 18.9978, b = 5.3802 c = 8.4385 Å, α = β = γ = 90° respectively. In the composition of x = 0.3 it was found that the phase of BaSrFe4O8 begin to form due to the overload expansion of the Sr2+ occupancy which made the distortion of the initial lattice parameters and finally in the x = 0.5 composition the single phase of BaSrFe4O8 was clearly formed. Energy Dispersive Spectroscopy (EDS) was used to confirm the change of the material structure by measuring the elemental compound composition ratio. The result of EDS spectra clearly exhibited the dominant elements were Barium (Ba), Strontium (Sr), Iron (Fe), and Oxygen (O) with the compound ratio (Atomic percentage and mass percentage) correspond to the BaFe2O4 and BaSrFe4O8 phase.

Properties of strontium doped barium titanate powder prepared by solid state reaction

Strontium doping material has been successfully doped to produce Barium Strontium Titanate (Ba1-xSrxTiO3) with variation in the percentage of moles of strontium 1%, 2%, 3%, 4% and 5% that processed by the solid state reaction method. Firstly, Ingredients (Barium carbonate, strontium carbonate and titanium oxide) have been mixed, milled during 6 hours to form solid powders. Then, sample pellets were pressed by mold machine which have been sintered in a furnace at 1100 °C during 2 hours. The properties of sample were observed using X-Ray Diffraction (XRD) for analyzing crystalline structure, Scanning Electron Microscopy (SEM) for showing morphological properties, RCL meter for dielectric constant. The XRD results indicated that the diffraction pattern is Ba1-xSrxTiO3 (BST) pattern. In addition, the results of General Structure Analysis System (GSAS) refinement with the Rietveld method showed that strontium doping has entered into Barium Titanate (BaTiO3). Increasing the number of moles of strontium has changed the lattice parameter and tertagonality of crystal BST. It affected the grain size and dielectric constant of BST too.

Crystallographic modeling and impedance studies of gadolinium modified La1−xGdxMnO3 (x = 0.1–0.3) ceramics

The crystal chemistry of perovskite structured ceramic phases: La0.9Gd0.1MnO3 (LMGd-1), La0.8Gd0.2MnO3 (LMGd-2) and La0.7Gd0.3MnO3 (LMGd-3) have been investigated using General Structure Analysis System (GSAS) programming. The LMGd phases crystallize in the space group R-3c and Z=6. Powder diffraction data have been subjected to Rietveld refinement to arrive at a satisfactory structural convergence of Rietveld parameters: Rp, Rwp and goodness of fit. Lattice parameters, bond lengths and bond angles have been calculated from GSAS software. Their electrical behaviour investigated by impedance spectroscopy in the frequency range 42Hz–5MHz at temperatures between 50° and 300°C. Nyquist plots show the dominance of grain contribution and Debye – like relaxation in the materials. Conductivity data as a function of temperature and frequency suggest semiconductor behavior of the materials.