Powder Patterns Research Articles

Synthesis and Crystal Structures of Two Crystalline Silicic Acids: Hydrated H-Apophyllite, H16Si16O40 • 8–10 H2O and H-Carletonite, H32Si64O144

Hydrated H-Apophyllite (HH-Apo) and H-carletonite (H-Car) were synthesized at 0 °C by leaching an apophyllite and a carletonite single crystal in a large surplus of 1.2 molar hydrochloric acid. The XRD powder patterns of HH-Apo and H-Car were indexed with space group symmetries of P4/ncc and I4/mcm and lattice parameters of a = 8.4872(2) Å, c = 16.8684(8) Å and a = 13.8972(3) Å, c = 20.4677(21) Å, respectively. The crystal structures were solved based on model building of the structures of the precursors and a physico-chemical characterization. Rietveld structure refinements confirmed the structure models. HH-Apo and H-Car are among the very few crystalline silicic acids whose structures have been determined and confirmed based on a structure refinement. The structure of HH-Apo contains thin silicate monolayers that can be regarded as constructed by rings of interconnected [SiO3OH] tetrahedra which form a puckered silicate layer. A sheet of water molecules is intercalated between the silicate layers. There are no direct hydrogen bonds between the silanol groups, but there are hydrogen bonds of different strengths between the terminal O atoms of the silicate layers and the intercalated water molecules. The 1H MAS NMR spectrum presents a strong signal at 4.9 ppm related to the aforementioned bonds and interactions between the water molecules, as well as a small signal at 22.5 ppm corresponding to an extremely strong hydrogen bond with d(O...O) ≈ 2.2 Å. The structure of H-Car is free of structural water and consists exclusively of microporous silicate double-layers with 4-connected [SiO4] and 3-connected [SiO3OH] tetrahedra in a ratio of 1:1 and a thickness of 9.2 Å. Neighboring layers are connected to each other by medium–strong hydrogen bonds with O...O distances of 2.56 Å. The structure of HH-Apo decays within several hours while H-Car is stable. A topotactic condensation reaction applied to H-Car forms an irregularly condensed silicate which still contains the layers in a distorted form as building blocks.

Microstructure and residual stress evolution during cyclic elastoplastic deformation of AISI316L fabricated via laser powder bed fusion

In metal additive manufacturing (MAM), microstructural properties such as texture, residual stresses, and dislocation density have emerged as key factors ruling the resulting mechanical performances. In this study, cylindrical AISI 316L specimens, fabricated with laser powder bed fusion (LPBF), were tested under cyclic elastoplastic (EP) deformation using a constant strain amplitude to highlight the evolution of residual stresses (RS), dislocation density and texture with increasing number of EP cycles, N, across the hardening-softening (H–S) transition stage, in the attempt to find correlations between relevant microstructural parameters and macroscopic properties. The structural and microstructural analysis is carried out through whole powder pattern modeling (WPPM) of neutron diffraction (ND) data and Electron Back-Scattering Diffraction (EBSD) analysis. The H–S transition is found to occur within 7–9 cycles, with RS fading out already after 5 cycles. Across the H–S transition, the trend of the maximum tensile stress correlates closely with the trend of WPPM-calculated total dislocation density, suggesting a major role of dislocations’ characteristics in the evolution of macroscopic mechanical properties. EBSD analysis reveals the rearrangement of geometrically necessary dislocations (GND) into cellular structures, and moderate grain refinement, which are deemed to be responsible for the quick fading of RS in the very early stage of EP loading. ND-based texture analysis reveals a (220) preferential orientation retained throughout the EP tests but with orientation density functions (ODFs) changing non-monotonically with N, suggesting preliminary partial randomization of grains around the deformation axis followed by the recovery of crystallographic anisotropy and more localized ODFs.

Crystal structure of nicarbazin, (C13H10N4O5)(C6H8N2O)

The crystal structure of nicarbazin has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Nicarbazin is a co-crystal of 4,4′-dinitrocarbanilide (DNC) and 2-hydroxy-4,6-dimethylpyrimidine (HDP) molecules. Nicarbazin crystallizes in space group P-1 (#2) with a = 6.90659(8), b = 12.0794(4), c = 13.5040(7) Å, α = 115.5709(11), β = 102.3658(6), γ = 91.9270(4)°, V = 982.466(5) Å3, and Z = 2. The DNC and HDP molecules are linked by two strong N–H⋯O and N–H⋯N hydrogen bonds, and the HDP molecules are linked into centrosymmetric dimers by another N–H⋯O hydrogen bond. These strong hydrogen bonds link the molecules into layers parallel to the ab-plane and parallel stacking of both DNC and HDP molecules is prominent in the structure. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®).

Three-dimensional electron diffraction on clinkers: the belite α'H incommensurate modulated structure.

Traditional X-ray methods are extensively applied to commercial cement samples in order to determine their physical and chemical properties. Powder patterns are routinely used to quantify the composition of these phase mixtures, but structure determination becomes difficult because of reflection overlapping caused by the high number of different crystal structures. The fast-growing 3D electron diffraction technique and its related automated acquisition protocols arise as a potentially very interesting tool for the cement industry, since they enable the fast and systematic acquisition of diffraction data from individual particles. In this context, electron diffraction has been used in the investigation of the different crystalline phases present in various commercial clinkers for cement. Automated data collection procedures and subsequent data processing have enabled the structural characterization of the different crystal structures from which the α'H polymorph of Ca2SiO4 (belite) exhibited satellite reflections. Its average crystal structure has been known since 1971 and satellite reflections have been reported previously, yet the modulation was never fully described by means of the superspace formalism. Here, the incommensurately modulated structure is solved and refined using harmonic and crenel functions in the superspace group Pnma(α00)0ss, showing the potential of 3D electron diffraction for systematic crystallographic characterizations of cement. A full description of the different belite polymorphs is provided considering this modulated structure.

Formation of Fe4+ based on the Fe-O bond lengths in perovskite Eu1-xSrxFeO3

The physical properties of high oxidation state of transition metal oxide compounds have attracted many research interest for its potential applications. A systematic investigation of Fe4+ in Eu1-xSrxFeO3 with x = 0, 0.1, 0.2, 0.3, and 0.4 has been carried out in polycrystalline form obtained using sol-gel method. The single phase of Eu1-xSrxFeO3 is observed up to x = 0.3. The X-Ray powder pattern for low Sr content of x = 0.1, is best refined by using EuFeO3 crystal structure with Sr occupied the Eu-site. On the other hand, for higher Sr contents, two phases of EuFeO3 and Eu1/3Sr2/3FeO3 are required to obtained the best refinement. The result of the refinements shows that the volume and the average bond lengths of Fe-O decreases as increasing the Sr content. These results are consistent to support the existence of Fe4+ upon Sr doping in Eu1-xSrxFeO3. For the Sr content of x = 0.1, an anomalous change of the volume is observed.

Proposed crystal structure of carbadox, C11H10N4O4

A model for the crystal structure of carbadox has been generated and refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Carbadox crystallizes in space group P21 (#4) with a = 13.8155(3), b = 21.4662(1), c = 16.3297(3) Å, β = 110.0931(7)°, V = 4548.10(3) Å3, and Z = 16. The crystal structure is characterized by approximately parallel stacking of the eight independent carbadox molecules parallel to the bc-plane. There are two different molecular configurations of the eight carbadox molecules; five are in the lower-energy configuration and three are in a ~10% higher-energy configuration. This arrangement likely achieves the lowest-energy crystalline packing via hydrogen bonding. Hydrogen bonds link the molecules both within and between the planes. Each of the amino groups forms a N–H⋯O hydrogen bond to an oxygen atom of the 1,4-dioxidoquinoxaline ring system of another molecule. The result is four pairs of hydrogen-bonded molecules, which form rings with graph set R2,2(14). Variation in specimen preparation can affect the preferred orientation of particles considerably. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®).

Crystal structure of indacaterol hydrogen maleate (C24H29N2O3)(HC4H2O4)

The crystal structure of indacaterol hydrogen maleate has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Indacaterol hydrogen maleate crystallizes in space group P-1 (#24) with a = 8.86616(9), b = 9.75866(21), c = 16.67848(36) Å, α = 102.6301(10), β = 94.1736(6), γ = 113.2644(2)°, V = 1273.095(7) Å3, and Z = 2 at 295 K. The crystal structure consists of layers of cations and anions parallel to the ab-plane. Traditional N–H⋯O and O–H⋯O hydrogen bonds link the cations and anions into chains along the a-axis. There is a strong intramolecular charge-assisted O–H⋯O hydrogen bond in the non-planar hydrogen maleate anion. There are also two C–H⋯O hydrogen bonds between the anion and cation. The cation makes a strong N–H⋯O hydrogen bond to the anion, but also acts as a hydrogen bond donor to an aromatic C in another cation. The amino group makes bifurcated N–H⋯O hydrogen bonds, one intramolecular and the other intermolecular. The hydroxyl group acts as a donor to another cation. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®).

Crystal structure of ractopamine hydrochloride, C18H24NO3Cl

The crystal structure of ractopamine hydrochloride has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional theory techniques. Ractopamine hydrochloride crystallizes in space group Pbca (#61) with a = 38.5871(49), b = 10.7691(3), c = 8.4003(2) Å, V = 3490.75(41) Å3, and Z = 8. The ractopamine cation contains two chiral centers, and the sample consists of a mixture of the S,S/R,R/S,R and R,S forms. Models for the two diastereomers S,S and S,R were refined, and yielded equivalent residuals, but the S,R form is significantly lower in energy. The crystal structure consists of layers of molecules parallel to the bc-plane. In each structure one of the H atoms on the protonated N atom acts as a donor in a strong discrete N–H⋯Cl hydrogen bond. Hydroxyl groups act as donors in O–H⋯Cl and O–H⋯O hydrogen bonds. Both the classical and C–H⋯Cl and C–H⋯O hydrogen bonds differ between the forms, helping to explain the large microstrain observed for the sample. The powder pattern has been submitted to ICDD® for inclusion in the Powder Diffraction File™ (PDF®).

DyIrSn and the Lu3Co2In4-type stannides Sm3Rh2Sn4 and RE 3Ir2Sn4 (RE = Y, Sm, Gd–Tm, Lu)

Abstract The Lu3Co2In4-type stannides RE 3Ir2Sn4 (RE = Y, Sm, Gd–Tm, Lu) were synthesized from the elements by arc-melting and subsequent annealing sequences in sealed silica ampoules. For a more comprehensive phase analytical study, the isotypic stannide Sm3Rh2Sn4 and the ZrNiAl-type stannides DyIrSn and LT-YIrSn were also obtained. The polycrystalline samples were characterized through their X-ray powder patterns. The structures of DyIrSn and Gd3Ir2.63(2)Sn3.37(2) (ZrNiAl type, space group P6‾2m), Sm3Ir2.52(2)Sn3.48(1), Gd3Ir2.49(1)Sn3.51(1) and Tm3Ir2.20(3)Sn3.80(3) (Lu3Co2In4 type, space group P6‾) were refined from single-crystal X-ray diffractometer data, revealing residual Ir/Sn disorder in the low-symmetry variants. The RE 3Ir2Sn4 stannides are derived from the equiatomic stannides REIrSn (≍RE 3Rh3Sn3) by partial Ir/Sn substitution. The symmetry reduction from space group P6‾2m to P6‾ is forced by the Ir/Sn ordering within the RE 6 trigonal prisms. The new Sn2 position shows the rare motif of a trigonal planar tin coordination with 289 pm Sn2–Sn1 distances (data for Gd3Ir2.49(1)Sn3.51(1)). 119Sn Mössbauer spectra confirm the two crystallographically independent tin sites in Tm3Ir2Sn4 and the structural disorder in Gd3Ir2Sn4.

Crystal structure of anthraquinone-2-carboxylic acid, C15H8O4

The crystal structure of anthraquinone-2-carboxylic acid has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional theory techniques. Anthraquinone-2-carboxylic acid crystallizes in space group P-1 (#2) with a = 3.7942(2), b = 13.266(5), c = 22.835(15) Å, α = 73.355(30), β = 89.486(6), γ = 86.061(1)°, V = 1098.50(7) Å3, and Z = 4. The crystal structure contains two independent molecules of anthraquinone-2-carboxylic acid. Although the expected hydrogen-bonded dimers are present, the dimers are not centrosymmetric. The dimer contains one molecule of each planar low-energy conformation. The crystal structure consists of a herringbone array of centrosymmetric pairs of molecules parallel to the bc-plane. The molecules stack along the short a-axis. The powder pattern has been submitted to ICDD® for inclusion in the Powder Diffraction File™ (PDF®).

Ca3Ru3Zn13 – a zinc-rich intermetallic phase composed of closest-packed layers

Abstract Ca3Ru3Zn13 was synthesized from the elements in a tantalum tube in a muffle furnace. The sample was annealed to 1123 K followed by slow cooling to enhance crystal growth. Ca3Ru3Zn13 was characterized through a Guinier powder pattern. The structure was refined from single crystal X-ray diffractometer data: new type, Pbcn, a = 522.92(5), b = 1792.72(14), c = 2789.6(2) pm, wR2 = 0.0590, 3451 F 2 values, 177 variables. One can describe the Ca3Ru3Zn13 structure by a stacking of closest packed layers of compositions Ca6Zn10, Ca6Zn12 and Ru6Zn15. The calcium atoms have high coordination numbers: Ca1@Zn13Ru3Ca2, Ca2@Zn15Ru4Ca, Ca3@Zn15Ru4Ca and Ca4@Zn15Ru4Ca. The shortest interatomic distances occur between the ruthenium and zinc atoms (255–273 pm). The Ru1@Zn8, Ru2@Zn10 and Ru3@Zn8 polyhedra condense via common edges to the [Ru3Zn13] substructure which hosts the calcium atoms. The zinc substructure consists of 15 crystallographically independent zinc sites with a broader range of Zn–Zn distances (255–307 pm).

Crystallographic Benchmarking on Diffraction Pattern Profiling of Polymorphs-TiO2 by WPPF for Pigment and Acrylic Paint

At a very low temperature high crystalline phase of TiO2 best-fitted strain anatase was synthesized by peptization which was the prime object of this study. Unresolved parameters were investigated by the X-ray diffraction (XRD) technique employed for lattice parameters, crystallite size, lattice volume, strain, crystal structure, d-spacing and percentage of phase in weight fraction. 54.40 % anatase, 29.10 % brookite and 16.50 % rutile crystalline phase were found by whole powder pattern fitting (WPPF-Rietveld’s refinement) method and lattice volume of anatase 137.150, brookite 267.079 and rutile 62.901 ų as well the crystal strain 0.307, 0.45 and 0.28 % of anatase, brookite and rutile polymorph-TiO2 found respectively. The calculated lattice parameters of the anatase are \(\alpha\)=\(\beta\)=\(\gamma\)= 90.0°; a=b= 3.8056 Å, c= 9.470 Å and predominant (101), (004) and (200) miller indices with diffracted angle (2Ɵ) 25.38, 37.26 and 48.22 observed. The average crystallite size was 7.39 nm which confirmed the formation of nano-crystal-TiO2 due to the highly dispersed on medium. The percentage of strain of the individual polymorphs of TiO2 shows the best fit used for the pigment and acrylic paint.

Valence tautomeric interconversion of bis-dioxolene cobalt complex with imino-pyridine functionalized by TEMPO moiety in solid solutions with isostructural nickel analogue: phase transitions and monocrystal destruction.

Valence tautomeric complexes (VT) are promising systems for creating molecular devices. From this viewpoint, valence tautomeric complexes with a hysteresis loop on the magnetic curve are of special interest as potential memory elements. The hysteresis loop is a consequence of retarded structural rearrangements which investigation is an actual problem. Recently, we have described a new VT transition taking place in a bis-dioxolene cobalt complex with imino-pyridine having a TEMPO substituent (A. A. Zolotukhin, et al., Inorg. Chem., 2017, 56, 14751-14754). Valence tautomeric transformation occurs with a hysteresis loop and is accompanied by a phase transition. The phase transition taking place during cooling is accompanied by crystal destruction. This fact makes it impossible to monitor the structural changes responsible for the hysteresis loop. The current research attempts to resolve this problem. A nickel compound of the same composition (TEMPO-imino-pyridine)Ni(3,6-DBSQ)2 was synthesized and characterized. It was established to be isostructural with the cobalt complex. It was used as an inert matrix for the dilution of the VT cobalt complex. The number of solid solutions with Co/Ni ratios of 1 : 1, 1 : 2, 1 : 4, and 1 : 8 was obtained. Variable temperature magnetic susceptibility measurements show that VT transformation with a hysteresis loop takes place in all solid solutions. The hysteresis loop is shifted to low temperatures primarily due to the shifting of its low-temperature boundary with dilution. The hysteresis width does not change significantly with dilution. DSC detected that transformations are accompanied by phase transitions at different temperatures at cooling and heating. The phase transition at the first cooling occurs at slightly lower temperatures compared with subsequent cycles. These temperatures correspond to the transition temperatures detected from the magnetic curves. The phase transition during the first cooling is accompanied by crystal destruction. Physical destruction takes place in the crystals of all solid solutions. X-ray diffraction powder patterns confirm that phase transition is accompanied by considerable reorganization of the crystal structure typical for the first order transitions. The unit cell volume of solid solutions is larger than that of pure complexes. Especially calculated crystal invariom indicated that the "lattice energy" in a solid solution is the lowest compared with that in "pure" nickel and cobalt complexes.

Accelerated acquisition of wideline solid-state NMR spectra of spin 3/2 nuclei by frequency-stepped indirect detection experiments.

73% of all NMR-active nuclei are quadrupolar nuclei with a nuclear spin I > 1/2. The broadening of the solid-state NMR signals by the quadrupolar interaction often leads to poor sensitivity and low resolution. In this work we present experimental and theoretical investigations of magic angle spinning (MAS) 1H{X} double-echo resonance-echo saturation-pulse double-resonance (DE-RESPDOR) and Y{X} J-resolved solid-state NMR experiments for the indirect detection of spin 3/2 quadrupolar nuclei (X = spin 3/2 nuclei, Y = spin 1/2 nuclei). In these experiments, the spectrum of the quadrupolar nucleus is reconstructed by plotting the observed dephasing of the detected spin as a function of the transmitter offset of the indirectly detected spin. Numerical simulations were used to investigate the achievable levels of dephasing and to predict the lineshapes of indirectly detected NMR spectra of the quadrupolar nucleus. We demonstrate 1H, 31P and 207Pb detection of 35Cl, 81Br, and 63Cu (I = 3/2) nuclei in trans-Cl2Pt(NH3)2 (transplatin), (CH3NH3)PbCl3 (methylammonium lead chloride, MAPbCl3), (CH3NH3)PbBr3 (methylammonium lead bromide, MAPbBr3) and CH3C(CH2PPh2)3CuI (1,1,1-tris(diphenylphosphinomethyl)ethane copper(I) iodide, triphosCuI), respectively. In all of these experiments, we were able to detect megahertz wide central transition or satellite transition powder patterns. Significant time savings and gains in sensitivity were attained in several test cases. Additionally, the indirect detection experiments provide valuable structural information because they confirm the presence of dipolar or scalar couplings between the detected nucleus and the quadrupolar nucleus of interest. Finally, numerical simulations suggest these methods are also potentially applicable to abundant spin 5/2 and spin 7/2 quadrupolar nuclei.

Computational study of band gap and structural effect of doped BiVO4

Density functional theory calculation using Quantum Espresso package was conducted to study band gap and structural effect of BiVO4 by doping elements like Zr, Mo and S, to substitute Bi, V and O. Band gap of BiVO4 has been reduced from 2.25 to 1.54 eV by ~8% S2- substitution with O2-. Distance between atoms V-O increased by changing to V-S, which effects vibration of the atoms in the structure. ~2% substitution Mo and Zr with Bi and V changed monoclinic BiVO4 to mix phase of tetragonal scheelite phase. It has been shown that XRD powder pattern of optimized structure can show (121) plane peak shifts by doping Mo or Zr in BiVO4 lattice.

Quantitative Determination of the Compositional Inhomogeneity in NMC Cathode Materials by Williamson-Hall Analysis

Over the past decades, the co-precipitation synthesis technique has been used, particularly for making LiNixMnyCozO2 (NMC) cathode materials for lithium-ion batteries (LIBs), due to better control of particle morphology and higher compositional homogeneity in the final NMC product compared to other methods. However, the co-precipitation method introduces complexity and consumes large amounts of energy and water, which can increase cost. This has led researchers to investigate solid-state NMC synthesis techniques in order to improve sustainability and reduce LIB cost [1-3]. Obtaining homogeneous mixing of transition metals at the atomic scale by solid-state methods remains a challenge. Since compositional homogeneity has a vital effect on the electrochemical performance of the NMCs, it is essential to quantitatively estimate the degree of inhomogeneity in cathode materials for the development of new synthesis methods.In the present study, a quantitative X-ray diffraction (XRD) analysis technique using the Williamson-Hall (WH) method is used to determine the degree of inhomogeneity in NMC precursors and NMC cathode materials. In this regard, single-phase rock salt (RS) precursors with varying degrees of transition metal homogeneity were prepared by combining NiO, MnO and CoO by grinding for different times, followed by heating under an Ar flow. Then, NMC cathode materials were made by heating the RS-precursors with lithium carbonate in air. EDS elemental maps showed that transition metal inhomogeneity existed in the RS-precursors and final NMCs and that this inhomogeneity is primarily associated with the Mn distribution (Figure 1(a)). Furthermore, the compositional inhomogeneity became reduced with increasing precursor grinding time.Using a WH analysis method, composition variation in the NMC precursor and in the final NMC product could be quantitatively determined from conventional XRD powder patterns. Utilizing this analysis, it was found that inhomogeneity in the precursor is translated into the final NMC, so that a similar trend in the degree of inhomogeneity was observed for both synthesized precursors and their NMC products (Figure 1(b) and (c)). Additionally, NMCs with high compositional homogeneity showed much better electrochemical performance compared to the samples with higher degree of inhomogeneity. We believe the proposed method is highly useful in the development of new cathode precursors and in predicting the performance of the NMC cathode materials by quantitatively determining their degree of compositional inhomogeneity.

Battery Thermalization for Operando Synchrotron Powder Diffraction: Application to the Ca-TiS2 System

Characterizing electrode materials and understanding its behavior during redox process is a key factor for battery improvement. In Situ techniques on Operando batteries are of particular interest since they do not only probe the material during the electrochemical process but avoid its hazardous and tedious extraction and transfer under inert atmosphere from an electrochemical cell to e.g. capillaries, to perform Ex Situ data collection. Synchrotron based techniques –absorption and diffraction – together with improved detectors, are now intensively used in such In Situ studies on Operando batteries since they allow fast and real time data acquisition during the electrochemical, ion (des-)insertion, process. So far most In Situ X-ray powder diffraction studies on Operando batteries are performed at room temperature using either coin cells or so called Leriche cells [1] (pouch cells, despite widely used for spectroscopy, are generally not favored for diffraction since the container material produce additional Bragg peaks). At ALBA we slightly modified both types of cells: Leriche type and more widespread used CR2032-type coin cells so as to perform data collection in temperature range -10° – 100° C. (see picture)Both types of cell have been used to study the intercalation of calcium in TiS2, previously determined by Ex Situ powder diffraction [2]. We managed to collect powder patterns operando at 60°C, 45°C and room temperature. (Des-)Insertion of solvated Ca2+ in TiS2 was favoured by temperature, its signature being the appearance of a new phase with a first diffraction peak at very low angles (~17.7 Å in terms of d-spacing). The process was found to be solvent dependent and reversible upon oxidation, which differs from Li cells where a similar process was observed.[3]Either of these thermalized cells can be used at CELLS-ALBA synchrotron for Power Diffraction on BL04-MSPD beamline or hard X-ray Absorption Spectroscopy (XANES/EXAFS) on BL22-CLEASS, and since 2023 also using simultaneous Powder Diffraction and hard X-ray Absorption Spectroscopy in BL16-NOTOS beamline. Moreover, the Leriche setup is also designed to fit for a use in laboratory X-ray diffractometers, in both reflection and transmission. Leriche et al. (2010). J. Electrochem. Soc., 157(5), A606-A610.Tchitchekova et al (2018). Chem. Mater 30, 847−856Houdeville et al. (2021). J. Electrochem. Soc., 168, 030514 Figure 1

Rare earth Gd3+ substituted on cobalt ferrites: Structural and dielectric studies by citrate gel autocombustion method

Gadolinium-doped cobalt ferrite (CoGdxFe2-xO4; X = 0–0.025 in a 0.005 interval) was synthesised using citrate gel autocombustion. The effect of Gd3+ ions on structural, dielectric, and magnetic characteristics has been investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, ultraviolet visible spectroscopy (UV), an impedance (dielectric) analyzer, and a vibrating sample magnetometer (VSM) were used to characterise the as-synthesised materials. X-ray diffraction powder patterns were used to confirm phase identification and spinel structure, and the Williamson-Hall plot was used to investigate the crystalline size and lattice strain on the peak broadening of each sample, with crystalline size ranging from 13 to 48 nm. The scanning electron microscopy (SEM) micrographs demonstrate particle agglomeration, while energy dispersive spectroscopy (EDAX) pictures indicate the purity and existence of all elements in the created material samples. The frequency-dependent dielectric constant, dielectric loss, and AC electrical conductivity in the frequency range 50 Hz–1 MHz. The behaviour of dielectric properties has been studied using the Maxwell-Wagner model and Koop's theory. Because of this, higher frequencies show less dielectric loss, making them appropriate for use in high-frequency device applications.

Tracking deactivation of zeolite beta with and without a detailed structure model: XRD analysis and in situ studies

This paper introduces two versatile new models for assessing the deactivation level of the industrially useful catalyst Beta zeolite. 1) a stacking disorder (SD) model: in which supercells built from stacked layers with refined faulting probability are generated, averaged and fitted to the powder pattern, and dummy carbon atoms in the pore system allow estimation of the degree of deactivation by coke; 2) a semi-empirical (SE) model: in which a reduced tetragonal unit cell is used to fit the sharp Bragg reflections in the PXRD pattern in a Le Bail-type fit and the broad, diffuse peaks are fitted individually to obtain intensities and positions. The reduced cell gives very precise lattice parameters, which can be determined quickly for a series of in situ data, while the ratio between the scale factor of the sharp reflection part in the model and the intensity of the first broad peak gives a measure of the degree of deactivation by coke. The models are validated, and their strengths and weaknesses compared by fitting of in situ PXRD data collected during temperature programmed oxidation of coke from two Beta zeolite samples fully deactivated in the MTH process. Analysis of such data from Beta zeolites has not been demonstrated before and could provide a convenient and useful tool for the chemical industry.

Calculating the reference intensity ratio of crystalline phases with unknown atomic arrangements using the lattice parameters and chemical information

The reference intensity ratio (RIR) is the intensity ratio of a specified peak of the target crystalline phase to a certain peak of the reference phase in the powder X-ray diffraction pattern of a mixture of the target and reference phases in a weight ratio of 1:1. The RIR represents the diffraction power of the target phase compared with that of the reference phase. A quantitative phase analysis (QPA) can be readily made on the basis of only a powder pattern when the RIR values of all component phases in the mixture are available. The RIR of a target phase can be measured experimentally or calculated in accordance with its crystal structure. RIR values are given in most powder diffraction files (PDFs) published by the International Centre for Diffraction Data, but there are still more than 110 000 PDFs for which the RIR is absent. Newly discovered phases may be present in a mixture as components of unknown weight fractions, for which the RIR values can be neither measured nor calculated with the currently available method. Herein is presented a new method of calculating the RIR of a crystalline phase from its lattice parameters, the chemical content of the unit cell and a list of normalized intensities of reflections over a sufficiently large diffraction angle range. The new method can be used to calculate not only the absent RIRs in the PDFs but also the RIR of a component phase of a mixture of unknown weight fraction when the lattice parameters and chemical content of the unit cell of the corresponding phase are known.