Synchrotron Radiation X-ray Diffraction Analyses Research Articles

Initial Growth Behavior in Catalyst-Free-Grown Vertical ZnO Nanorods on c-Al2O3, as Observed Using Synchrotron Radiation X-ray Scattering

In this study, synchrotron radiation X-ray diffraction analysis is used to investigate the initial growth dynamics of metal–organic vapor-phase epitaxy-grown ZnO nanorods on c-Al2O3 substrates. A two-dimensional area detector with a grazing-incidence geometry enables projected reciprocal space mapping (RSM) using coordinate transformation of diffraction images. The projected RSM reveals multiple heteroepitaxial relationships between ZnO and Al2O3, including the dominant relationship of ZnO(101̅0)∥Al2O3(21̅1̅0). Evolution of internal strain is revealed by an additional study on diffraction images and θ–2θ scans. Surface topology from atomic force microscopy estimates the growth rate, supported by the Scherrer equation analysis of the θ–2θ diffraction.

Correlation between Phase Behavior and Electrical Conductivity of 10 mol % Y-Doped BaZrO3: An Anomalous Dispersion Effect-Aided Synchrotron Radiation XRD Study Combined with TEM Observation and Electrochemical Analysis.

Y-doped BaZrO3 (BZY) has high proton conductivity and is a promising electrolyte candidate for fuel cells and electrolytic cells at an intermediate temperature range. However, the conductivity of BZY has a large discrepancy in the literature. In particular, for BaZr0.9Y0.1O3-δ (BZY10), the reported bulk conductivity varies in the range of more than 2 orders of magnitude. With the aim of revealing the reason, in this work, we conducted synchrotron radiation X-ray diffraction analysis on a BZY10. The X-ray was adjusted to 17.027 keV to approach the Y-K absorption edge (17.037 keV), and the anomalous dispersion effect was thereby activated for a precise distinction between Zr and Y. High-resolution scanning transmission electron microscopy observation and electrochemical measurements were also performed. Assisted by these experimental results, Rietveld refinement with greatly improved quality was thereby available to generate precise information on both the phase behavior and crystal structure. The results revealed that the BZY10 samples after sintering at 1600 °C for 8 to 200 h have a bimodal microstructure. They were not single phases, but mixtures of two perovskite phases differing slightly in Y contents. The Y contents in the two phases after sintering for 8 h were about 12.3 and 8.7 mol %, respectively, and finally became 10.6 and 9.2 mol %, respectively, after sintering for 200 h. In addition, the partition of Y over both the Ba and Zr sites was not suggested, although small Ba-deficiency around 0.05 formed in the sample sintered for 40 h or longer. But notably, the formation of the Ba vacancies is reasonably believed as the possible reason for the decrease in bulk and also grain boundary conductivities.

First platinum(ii)–alkaline-earth acetate-bridged complexes Ptii(m-OAc)4Mii(AcOH)4 (M = Ca, Sr, Ba)

The first platinum(ii)–alkaline-earth acetate-bridged complexes Ptii(m-OAc)4Mii(AcOH)4 (M = Ca, Sr, Ba) were synthesized, structurally characterized using single-crystal synchrotron radiation X-ray diffraction analysis and tested for catalytic performance in homogeneous styrene hydrogenation under mild conditions.

Great Disparity in Photoluminesence Quantum Yields of Colloidal CsPbBr3Nanocrystals with Varied Shape: The Effect of Crystal Lattice Strain

Understanding the big discrepancy in the photoluminesence quantum yields (PLQYs) of nanoscale colloidal materials with varied morphologies is of great significance to its property optimization and functional application. Using different shaped CsPbBr3 nanocrystals with the same fabrication processes as model, quantitative synchrotron radiation X-ray diffraction analysis reveals the increasing trend in lattice strain values of the nanocrystals: nanocube, nanoplate, nanowire. Furthermore, transient spectroscopic measurements reveal the same trend in the defect quantities of these nanocrystals. These experimental results unambiguously point out that large lattice strain existing in CsPbBr3 nanoparticles induces more crystal defects and thus decreases the PLQY, implying that lattice strain is a key factor other than the surface defect to dominate the PLQY of colloidal photoluminesence materials.

Centimeter-sized epitaxial h-BN films

We report the growth and transfer of centimeter-sized, epitaxial hexagonal boron nitride (h-BN) few-layer films using Ni(111) single-crystal substrates. The h-BN films were heteroepitaxially grown on 10 × 10 mm2 or 20 × 20 mm2 Ni(111) substrates using atmospheric pressure chemical vapor deposition with a single ammonia-borane precursor. The grown films were transferred to arbitrary substrates via an electrochemical delamination technique, and the remaining Ni(111) substrates were repeatedly re-used. A careful analysis of the growth parameters revealed that the crystallinity and area coverage of the h-BN films were mostly sensitive to the sublimation temperature of the ammonia-borane source. Moreover, various physical characterizations confirmed that the grown films exhibited the typical characteristics of hexagonal boron nitride layers over the entire area. Furthermore, the heteroepitaxial relationship between h-BN and Ni(111) and the overall crystallinity of the film were thoroughly investigated using a synchrotron radiation X-ray diffraction analysis including θ–2θ scans, grazing incident diffraction, and reciprocal space mapping. The crystallinity at the microscopic scale was further investigated using transmission electron microscopy (TEM)-based techniques, including selective area electron diffraction pattern mapping, electron back-scattered diffraction, and high-resolution TEM. Transparent and flexible ceramic films for electronic devices can now be made at centimetre scales by a low-cost technique. Hexagonal boron nitride (h-BN) crystals are attractive platforms for building next-generation circuits because their flat, graphite-like surfaces resist mechanical and chemical damage while offering excellent signal isolation. Gyu-Chul Yi from Seoul National University and colleagues have developed a way to improve large-scale manufacturing of these films using a reusable nickel template. Nickel has a surface structure that helps h-BN films grow with high crystallinity following chemical vapor deposition, but detaching the resulting ceramic layer has always proved troublesome. The Korean team solved this problem through an electrochemical delamination process that seamlessly separates h-BN films with dimensions up to 20 × 20 square millimetres using a stream of hydrogen bubbles. Centimeter-sized, epitaxial hexagonal boron nitride (h-BN) few-layer films were heteroepitaxially grown on Ni(111) single-crystal substrates using atmospheric pressure chemical vapor deposition with ammonia-borane single precursor. The grown films were transferred to arbitrary substrates via an electrochemical delamination technique, and the remaining Ni(111) substrates were repeatedly re-used. Over repeated growth and transfer after the initial annealing, no significant degradation of Ni(111) substrates was observed and the crystallinity of h-BN layers was reproduced reliably. The grown h-BN films showed typical physical characteristics of h-BN, with a high uniformity over a wide area. The large-area synthesis and transfer of atomically thin uniform epitaxial h-BN layers can be applied in various fields where high quality two-dimensional insulating layers are required.

Fabrication of Ni–Al nanoparticles via vacuum arc plasma evaporation and their catalytic properties for CO oxidation

Ni–Al nanoparticles were fabricated from Ni3Al-based alloys using vacuum arc plasma evaporation, and their catalytic activities for carbon monoxide (CO) oxidation were examined. The synthesized nanoparticles were characterized in detail using synchrotron radiation X-ray diffraction analyses, scanning transmission electron microscopy, and surface area measurements based on nitrogen adsorption. The as-fabricated nanoparticles were composed of Ni, Ni3Al, and a small amount of NiAl, with Al2O3 and NiO phases formed on their surfaces. The nanoparticles exhibited a much higher activity than that of a conventional atomized Ni3Al powder. It was found that the Ni phase is oxidized to NiO during CO oxidation, while the Ni3Al phase remains unchanged. It is likely that the NiO phase serves as the active species for CO oxidation, and the Ni3Al and Al2O3 phases serve as supports for the NiO phase.

Crystal Structural Analyses of Ferrielectric Tetragonal (Bi1/2Na1/2)TiO3–7%BaTiO3 Powders and Single Crystals

We have investigated the crystal structure of (Bi1/2Na1/2)TiO3–7%BaTiO3 (BNT–7%BT) by high-resolution neutron powder diffraction (NPD) and high-energy synchrotron radiation X-ray diffraction (SR-XRD) analyses. The NPD study revealed that the BNT–7%BT crystals have a single-phase tetragonal structure with P4bm symmetry. The crystal structure refined by the Rietveld method was found to be similar to the ferrielectric P4bm phase reported for BNT at a high temperature of 673 K. The SR-XRD analyses for single crystals of BNT–7%BT demonstrated that the P4bm phase remains as a stable phase in the crystals even after a high electric field is applied for poling, which is different from the structural analysis of ceramics by Ma et al. [Phys. Rev. Lett. 109 (2012) 107602].

Electroactive Nanotubes from π-Conjugated Discotic Molecules

Abstract Self-assembly of π-conjugated molecules is attractive for construction of well-defined, nanometer-scale electroactive materials. This account describes our developments on self-assembled nanotubes from Gemini-shaped hexa-peri-hexabenzocoronenes (HBCs). At first, detailed molecular arrangement in the nanotube is presented, which is perfectly revealed by a synchrotron radiation X-ray diffraction analysis of a macroscopic fiber consisting of highly aligned HBC nanotubes. Next, electroconductive properties of the HBC nanotubes are investigated. By means of direct current and noncontact methods, anisotropic charge-transport properties in the nanotubes are confirmed. The effect of the surface oligoether chains on intertubular conduction is also examined by field-effect transistor measurements. Finally, optoelectronic applications are developed by constructing newly designed nanotubes. These nanotubes possess a coaxial configuration, where an electron-donating graphitic bilayer of π-stacked HBC arrays is laminated by an electron-accepting molecular layer. Due to the molecular-layer donor/acceptor heterojunction, the nanotubes exhibit remarkable photoconduction and photovoltaic outputs. Furthermore, the optoelectronic properties are modulated by changing the density of electron acceptors on the nanotube surfaces by coassembly of multiple components or utilizing photochromism. These results will advance to electronic and optoelectronic applications of supramolecular nanomaterials.

Synchrotron radiation X-ray diffraction analysis for Bi-based oxide superconducting wire

The Bi-based oxide superconducting wire is one of the most promising materials for practical uses such as electric power transmission, electromagnets and so on. For the higher performances required in these applications, it is necessary to increase the critical current (Ic). We have carried out synchrotron radiation X-ray diffraction analysis to improve our manufacturing processes and thus to achieve higher Ic. We have performed in situ X-ray diffraction measurements during the sintering and cooling processes, and observed the decrease of Bi-2223(=(Bi,Pb)2Sr2Ca2Cu3Ox) phase during the cooling process. We have also evaluated the distribution of the crystal orientation in whole wire thickness, by measuring the rocking curves. We have observed that the distribution of the crystal orientation is improved by a refinement of the process conditions.

Investigation of Neolithic ceramic pigments using synchrotron radiation X-ray diffraction

Crystalline phases present in pigments scratched off the surfaces of some decorated ceramic sherds belonging to the Cucuteni Neolithic culture were successfully identified using synchrotron radiation X-ray diffraction at Daresbury Laboratory. The ceramic sherds were selected from a collection of the National Museum of Romanian History in Bucharest. The synchrotron radiation X-ray diffraction analysis revealed that the black-color pigments on the surface of a number of sherds were produced by a variety of jacobsite (Fe2MnO4) phases; magnetite (Fe3O4) was also found in one of the sherds. The red color was derived from clay slips with a high content of hematite (Fe2O3). Calcite (CaCO3) was found in the white pigments; its presence was explained as being related to postburial deposition processes. Conclusions on technological aspects, provenance, and conservation issues are given.

Formation history of CI-like phyllosilicate-rich clasts in the Tsukuba meteorite inferred from mineralogy and noble gas signatures

Fine-grained, angular black clasts with longest dimensions up to 800 μm were found, dispersed in a brecciated region in the Tsukuba meteorite. The clasts, much darker than the dark portions of the light–dark structure in the Tsukuba host, are characterized by the presence of plaquette, spherulitic, and framboidal magnetites and pseudo-hexagonal pyrrhotite. Synchrotron radiation X-ray diffraction analyses showed that the major silicate phases in the clasts are saponite and serpentine. Transmission electron microscopy (TEM) revealed that the phyllosilicates have compositions quite similar to those in the Orgueil CI carbonaceous chondrite. Therefore, mineralogically and chemically, the clasts resemble CI chondrites and are quite different from the host H5-6 chondrite Tsukuba. The clasts serve as an indicator of temperatures during regolith lithification of the Tsukuba parent body, because their mineralogy and noble gas compositions are subject to change during weak heating. The 001 basal spacing of saponite in the clast is 13.2 Å, which indicates that saponite retains interlayer water molecules. This observation and the presence of serpentine suggest that the clasts, as a whole, have never been heated above 500°C. Noble gas analyses showed that the clasts contain large amounts of solar and primordial noble gases. The results of stepwise heating analyses indicate that no apparent thermal loss of noble gases from the clasts occurred, consistent with the mineralogical evidence. TEM observation revealed that the periphery of a clast was transformed into amorphous phases, indicating that only the periphery was heated to 700°C. Based on the results of our analyses, the formation history of the clasts can be evaluated as follows. Constituents of the clasts had been exposed to solar wind on the surface of the CI-chondrite-like parent body and formed the clasts. After ejection from the CI-like parent body, the CI-like meteoroid accreted to the Tsukuba parent body after early thermal metamorphism that reached 700–1000°C. The clasts must have been located in the regolith, because they were found among the light–dark structure in the meteorite and contain abundant solar noble gases. Impacts into the regolith have crushed the clasts into smaller pieces and probably induced lithification of the regolith material. During lithification, the peripheries of the clasts were heated briefly to 700°C, but the temperature of the interior of the clasts has never exceeded 500°C. This is the first evidence constraining temperature during lithification of the ordinary-chondrite parent-body regolith. Finally, the Tsukuba meteoroid, including the CI-like clasts, was ejected from the Tsukuba parent body and fell onto the Earth after a transit time of 8.1 Ma.