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BackgroundCharacterizing the microstructure evolution of materials during the gas-solid reaction is crucial for the comprehensive understanding of the reaction mechanism. In situ synchrotron X-ray diffraction (XRD) is a powerful tool for this purpose. For the reactions involving corrosive gases, unique devices need to be designed for the in situ experiments.PurposeThe study aims to develop two kinds of in situ synchrotron XRD devices for characterizing gas-solid reaction.MethodsLiquid volatilization and solid heat treatment were applied respectively to the generation of reaction gas for two kinds of in situ synchrotron XRD devices. The gas-solid reaction in liquid volatilization was triggered and precisely controlled by injecting liquid into the cell, suitable for gas-solid reaction at room temperature and near atmospheric pressure. For in situ XRD characterization device with reaction gas generated by heat treatment of solid, both the cell and the X-ray window were made of quartz glass, hence suitable for the gas-solid reaction temperature up to 450 ℃ and X-ray photon energy above 18 keV.Results & ConclusionsThe two in situ devices have the advantages of compact, disassemble and reusable. These devices help to facilitate the application of synchrotron experimental techniques for in situ characterization of chemical reaction processes.

Vertically aligned nanocomposite films hold the promise of making a significant contribution to the performance enhancement and multifunctional integration of flexible thin-film devices but are hindered by the difficulty of direct epitaxial growth on flexible substrates. In this work, freestanding BaTiO3–CeO2 epitaxial nanocomposite membranes were prepared by using water-soluble Sr3Al2O6 as the sacrificial buffer during film deposition. The membrane's lattice parameters as well as their epitaxial relationship, before and after its removal from the single-crystal substrates, were quantitatively measured and analyzed by combining x-ray diffraction and TEM. In addition, synchrotron soft x-ray absorption spectroscopy reveals the discrepancy in the surface and internal electron states of Ce and Ti via comparative studies in total electron yield mode and transmission mode, respectively. This work exemplified that freestanding membranes provide a convenient platform for (1) the study of in-plane lattice information of epitaxial oxide films via TEM and for (2) the comparative study of surface and internal electron band information of epitaxial oxide films. [ABSTRACT FROM AUTHOR]

The generation and control of multiple phases via hydrogen insertion open up avenues for tuning the properties of transition metal oxides. Here, by employing both in situ x-ray diffractions and in situ electrical measurements, we accurately probed the full structural phase transitions during the reversible process of hydrogen insertion into and extraction from the vanadium dioxide lattice. Repeatable switches between the hydrogenated VO2 phases and the pristine VO2 phase were demonstrated, implying potential applications for hydrogen detection/storage and multi-state information memorizers. Moreover, different phases were further discussed by synchrotron x-ray absorption spectroscopy and theoretical first-principles calculations, which reveal that hydrogen insertion greatly affects the filling of the d-band as well as the electrical properties. This work will provide fundamental insight into the comprehensive understanding of hydrogen-induced phase transition in metal oxides and may guide the development of proton-based sensors and devices. [ABSTRACT FROM AUTHOR]

Identifying a suitable water-soluble sacrificial layer is crucial to fabricating large-scale freestanding oxide membranes, which offer attractive functionalities and integrations with advanced semiconductor technologies. Here, we introduce a water-soluble sacrificial layer, "super-tetragonal" Sr 4 Al 2 O 7 (SAO T ). The low-symmetric crystal structure enables a superior capability to sustain epitaxial strain, allowing for broad tunability in lattice constants. The resultant structural coherency and defect-free interface in perovskite ABO 3 /SAO T heterostructures effectively restrain crack formation during the water release of freestanding oxide membranes. For a variety of nonferroelectric oxide membranes, the crack-free areas can span up to a millimeter in scale. This compelling feature, combined with the inherent high water solubility, makes SAO T a versatile and feasible sacrificial layer for producing high-quality freestanding oxide membranes, thereby boosting their potential for innovative device applications.

Effective control of heat transfer is vital for energy saving and carbon emission reduction. In contrast to achievements in electrical conduction, active control of heat transfer is much more challenging. Ferroelectrics are promising candidates for thermal switching as a result of their tunable domain structures. However, switching ratios in ferroelectrics are low (<1.2). We report that high-quality antiferroelectric PbZrO 3 epitaxial thin films exhibit high-contrast (>2.2), fast-speed (<150 nanoseconds), and long-lifetime (>10 7 ) thermal switching under a small voltage (<10 V). In situ reciprocal space mapping and atomistic modelings reveal that the field-driven antiferroelectric-ferroelectric phase transition induces a substantial change of primitive cell size, which modulates phonon-phonon scattering phase space drastically and results in high switching ratio. These results advance the concept of thermal transport control in ferroic materials.

3D crystalline order with 1 nm resolution is observed in aqueous solutions of supramolecular nanotubes containing 94 % water, at concentrations as low as 6 wt%. 50 of star-like organic ions arrange into supramolecular rings which, in turn, stack on top of each other to form long hollow tubes with 15 nm outer diameter. Cryo-TEM and X-ray diffraction show that the parallel nanotubes arrange on a perfect hexagonal lattice. Unexpectedly, fiber diffraction on sheared solutions revealed numerous hkl Bragg reflections on several layer lines indicating longitudinal interlock between the tubes and 3D crystalline order with molecular-scale details transferred across 10 nm thick layers of water. The observed high 3D order is attributed to long-range attraction between like-charged tubes and amplified charge modulation by the extremely high intra-tube correlation length., (© 2023 Wiley-VCH GmbH.)

Multiferroics with simultaneous electric and magnetic orderings are highly desirable for sensing, actuation, data storage, and bio-inspired systems, yet developing flexible materials with robust multiferroic properties at room temperature is a long-term challenge. Utilizing water-soluble Sr 3 Al 2 O 6 as a sacrificial layer, the authors have successfully self-assembled a freestanding BaTiO 3 -CoFe 2 O 4 heteroepitaxial nanostructure via pulse laser deposition, and confirmed its epitaxial growth in both out-of-plane and in-plane directions, with highly ordered CoFe 2 O 4 nanopillars embedded in a single crystalline BaTiO 3 matrix free of substrate constraint. The freestanding nanostructure enjoys super flexibility and mechanical integrity, not only capable of spontaneously curving into a roll, but can also be bent with a radius as small as 4.23 µm. Moreover, piezoelectricity and ferromagnetism are demonstrated at both microscopic and macroscopic scales, confirming its robust multiferroicity at room temperature. This work establishes an effective route for flexible multiferroic materials, which have the potential for various practical applications., (© 2021 Wiley-VCH GmbH.)