High-resolution X-ray diffraction is applied to investigate macro and micro crystal structure changes across different synthesis routes in BNBT4 piezoceramics. Synthetic powders were obtained by ...conventional sol-gel auto combustion and mixed oxides methods; then samples were sintered by combining hot uniaxial pressing and subsequent recrystallization. The crystal structure of the ceramic obtained by sol-gel is rhombohedral (R3c) and the one obtained from mixed oxides is monoclinic (Cc). In the sol-gel case, a poling process produces an intense 001 texture parallel to the polarizing electric field. Poling the mixed oxides ceramics quickly transforms the structure from monoclinic to rhombohedral while texture and anisotropic micro-strains develop further as the poling increases. A correlation between detected structural transformations and variations in selected physical properties is suggested. The anisotropy of the critical temperatures for dielectric and electromechanical depolarization is lower for mixed oxides ceramics than for sol-gel ceramics.
Changes in crystal structure, microstructure and properties of (Bi0.5Na0.5)0.96Ba0.04TiO3 (BNBT4) piezoceramics, as dependent on sample physico-chemical route, are explored via high-resolution synchrotron XRD. Display omitted
•Synchrotron XRD detects crystal structure subtleties induced by synthesis processes.•Poling the mixed oxides ceramic transforms crystals from monoclinic to rhombohedral.•Poling the sol-gel ceramic textures the crystal parallel to the polarizing electric field.•Sol-gel high texture - high dielectric and electromechanical thermal depolarization anisotropy.•Mixed oxides high micro-strain - high electromechanical thermal depolarization delay.
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In this study, a nanostructured perovskite SmCoO3 material was successfully synthesized at ambient temperature using the mechanical alloying (MA) technique. A powdered mixture of samarium and pure ...metallic cobalt (Co) precursors was subjected to 24 h of milling to achieve the intended sample. The phase transformations induced by high-energy milling were investigated through ex situ X-Ray Diffraction (XRD) measurements and analyzed using the Rietveld method. Some properties of SmCoO3 were examined using techniques such as Differential Scanning Calorimetry (DSC), heat treatment, XRF (X-Ray Fluorescence), and UVVis absorbance. These comprehensive characterizations provide valuable insights into the synthesis and properties of nanostructured SmCoO3 perovskite, facilitating its potential applications in various fields.
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•Green synthesis: SmCoO3 perovskite achieved without heating.•Thermal stability unveiled: DSC analysis reveals cobalt absorption.•Electronic insights: UVVis spectroscopy reveals multiple transitions.
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3.
The Rietveld method Rietveld, Hugo M
Physica scripta,
09/2014, Volume:
89, Issue:
9
Journal Article
Peer reviewed
Open access
A summary is given of the development of an improved method to handle powder diffraction data. The resulting method, now called the Rietveld method, uses powder diffraction step-scanned intensities ...instead of integrated powder intensities. This enables the full use of the information content of a powder diagram. The method has revitalized the use of powder diffraction in structure determination. An unexpected and later development is the use of the method in quantitative phase analysis. This is now an essential tool in many industrial processes.
Extracted from a tuberous root of the Amazon forest named Ariá (Goeppertia allouia), starch samples were submitted to four γ-radiation doses of 1, 5, 20 and 50 kGy and investigated by powder X-ray ...diffraction (XRD) and pasting properties. The XRD patterns were quantified by the Rietveld refinement method and the pasting properties by Palabiyik's, Hill's and Arrhenius models. Crystallinity values were obtained considering the semi-crystalline microstructures (mean crystallites sizes and microstrains) and the weight fraction of the semi-crystalline phases were calculated considering the diffuse X-ray scattering. The combination of the techniques revealed that the increase in the amorphous component is related to the continuous degradation of the semi-crystalline phases in lower molecular weight sugars that also increased pasting temperature and delaying the gelation process. The reduction in the activation energy of the phase transition is associated with the accumulated energy in the defects, induced by γ-radiation.
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•Starch from Ariá was subjected to γ-radiation and identified as C-type starch, composed of the A-type and B-type polymorphs.•A new approach was proposed to quantify the phase content and crystallinity of starches using XRD and Rietveld method.•The amorphous component increases with the growth of small sugar molecules generated by amylopectin chain breakage.•The γ-radiation dose progressively influences the physicochemical properties of Ariá starch.•Irradiation promoted partial dextrinization of the sample, influencing the physicochemical properties of the starch.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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6.
Hugo Rietveld (1932-2016) Hewat, Alan; David, William I. F.; van Eijck, Lambert
Journal of applied crystallography,
08/2016, Volume:
49, Issue:
4
Journal Article
Peer reviewed
Obituary for Hugo Rietveld.
Obituary for Hugo Rietveld.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
We investigated a nanostructured composite of α-Bi2O3/NiBi3, which was synthesized through high-energy milling, under high-pressure conditions of up to 30 GPa. To track its structural changes, we ...employed in-situ synchrotron angle-dispersive X-ray diffraction measurements in conjunction with density functional theory calculations. Crystallographic information was derived using the Rietveld method and DFT computations. Additionally, we examined the chemical short-range order using pair distribution functions and determined the compressibility parameters through the Birch-Murnaghan equation of state.
We explored the high-pressure behavior of a nanostructured composite of α-Bi2O3/NiBi3, applying pressures up to 30 GPa. The composite sample, synthesized by mechanical alloying, underwent thorough structural characterization by X-ray diffraction, high-resolution transmission electron microscopy and Raman spectroscopy. The sample's response to applied pressure was studied by analyzing crystallographic data obtained from in-situ synchrotron angle-dispersive X-ray diffraction measurements and density functional theory calculations. Crystallographic information from experiments was refined using the Rietveld method. Additionally, chemical short-range order was examined using pair distribution functions, and compressibility parameters were determined via the Birch-Murnaghan equation of state. This investigation into the high-pressure behavior of NiBi3 provides valuable insights for future studies and potential applications of similar materials in extreme pressure environments.
•NiBi3/α-Bi2O3 composite defies predictions, stable under 30 GPa, showcasing high-pressure resilience.•Versatile NiBi3 synthesis methods promise energy storage applications, adapting to diverse needs.•NiBi3 crystal behavior under pressure revealed by ADXRD and DFT, enhancing analysis tools for real-space insights.•Insights for high-pressure material tech, shaping future applications and tech strides.
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Mebendazole (MBZ) is a broad-spectrum active pharmaceutical ingredient (API) indicated for treating parasitosis, and it has three solid-state forms, A, B, and C. These solid forms exhibit significant ...differences in dissolution properties, which cause considerable changes in the therapeutic effect. When at least 30 % of Form A is present in the formulation, it has a similar effect to the placebo. The aim of this study was to develop a reliable quantitative method for MBZ (Forms A and C) suspensions that allowed to study the solid-state stability and the kinetics of the solid-state transformation of MBZ suspensions under the recommended pharmaceutical industry conditions. One method was developed to carry out the drying process and the other one to quantify Forms A and C of MBZ suspensions; both were evaluated. For the stability study, samples were prepared with different starting reference concentrations of Form A and stored from 1 to 24 months under long-term stability conditions (30 ± 2 °C and 75 ± 5 % RH) and from 1 to 6 months under accelerated stability conditions (40 ± 2 °C and 75 ± 5 % RH). Data collection was performed by powder X-ray diffraction (PXRD). The Rietveld method (RM) and Topas's program were used to solid form quantification. Avrami's equation was used to determine the kinetic parameters. The results showed that the combination of the drying process and solid form quantification developed method for suspension was a very accurate methodology for solid-state stability studies. Furthermore, in long-term and accelerated solid-state conditions, suspension with an initial value of 1 % of Form A were sufficient to cause a solid-state transformation (Form C to A) greater than 30 % in the first and second months, with a complete transformation in nine and six months respectively. These results demonstrate that suspensions show complete solid-state transformation (Form C to A) in a shorter time than the product's shelf life (∼2 years). In this work, a reliable methodology was developed to quantify MBZ (Forms A and C) suspensions. This methodology could be used to control the different solid forms for MBZ and other APIs to avoid solid-state transformation problems.
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Ternary sulfides BaPrCuS3 and BaSmCuS3 are first synthesized by the sulphidation reaction of a mixture of related oxides and metal Cu in a flow of (CS2, H2S) at 1170 K. The crystal structures of ...BaPrCuS3 and BaSmCuS3 are obtained by Rietveld method. BaPrCuS3 crystallizes in space group Pnma with unit cell parameters a = 10.56074(6), b = 4.11305(2) and c = 13.42845(7) Å, V = 583.289 (5) Å3, Z = 2 (structure type Eu2CuS3). BaSmCuS3 crystallizes in space group Cmcm with unit cell parameters a = 4.07269(4), b = 13.4499(1) and c = 10.3704(1) Å, V = 568.06 (1) Å3, Z = 2 (structure type KZrCuS3). The structural model is proposed for the Cmcm→Pnma transition in ABCX3 (X = S, Se) compounds for the sequence Sm-Pm-Nd-Pr. The dimensionless tolerance factor t = IR(A) × IR(C)/IR(B)2 is suggested to control the boundary between the Cmcm and Pnma structures. The micromorphological, thermal and spectroscopic properties are evaluated for BaPrCuS3. The compound melts incongruently at Tmelt = 1580.9 K. In BaPrCuS3, the band gap is estimated to be 2.1 eV. The vibrational parameters of BaPrCuS3 and BaSmCuS3 are comparatively observed by Raman spectroscopy.
•Ternary sulfides BaPrCuS3 and BaSmCuS3 are first synthesized by the sulphidation reaction.•The BaPrCuS3 and BaSmCuS3 compounds crystallized in space groups Pnma and Cmcm, respectively.•The vibrational parameters of BaPrCuS3 and BaSmCuS3 are comparatively observed by Raman spectroscopy.
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With high‐temperature solid‐state reaction method, a series of Lu2Sr(1−x)Al4SiO12:xEu2+ phosphors have been synthesized. With Rietveld refinement method, the crystal structure of Lu2SrAl4SiO12 has ...been refined. Under the excitation of the ultraviolet and violet band light, Lu2Sr(1−x)Al4SiO12:xEu2+ emits the Eu2+ characteristic blue broadband light. The photoluminescence properties of concentration quenching, emission peak shift, reflectance spectra, and luminescence decay have been investigated. With the structure analyses, the corresponding physical mechanisms have been discussed. With the increased temperature, this phosphor shows well thermal stabilities. For the xEu = 0.06, 0.08, and 0.1 phosphors, the strong anti‐thermal quenching performance has been observed. The reason for the anti‐thermal quenching of this phosphor has been discussed. The trap capture mechanism may be the suitable physical mechanism to explain the anti‐thermal quenching of this phosphor. This phosphor shows the potential applications in the white LED lighting fields.
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