Recent advances in layered (Fe‐based and Bi‐based) chalcogenides as superconductors or functional materials are reviewed. The Fe–chalcogenide (FeCh) family are the simplest Fe‐based high‐Tc superconductors. The superconductivity in the FeCh family is sensitive to external or chemical pressure, and high Tc is attained when the local structure (anion height) is optimized. The Bi–chalcogenide (BiCh2) family are a new group of layered superconductors with a wide variety of stacking structures. Their physical properties are also sensitive to external or chemical pressure. Recently, we revealed that the emergence of superconductivity and the Tc in this family correlate with the in‐plane chemical pressure. Since the flexibility of crystal structure and electronic states are an advantage of the BiCh2 family for designing functionalities, I briefly review recent developments in this family as not only superconductors but also other functional materials.
In this communication we report the synthesis, structural and preliminary physical characterisation of a new layered oxyselenide Ce(2)O(2)FeSe(2). This material, containing a 1D portion of the structure of the layered FeSe-related superconductors, is a semiconductor with a band gap of around 0.64 eV and orders antiferromagnetically at low temperatures. 相似文献
A new layered silicate has been synthesized in the quaternary system Na2O–SiO2–H2O-polymeric organic cation. The polymeric organic cation was intercalated into the silicate during crystallization. Composition, structure, and x-ray diffraction pattern of the new silicate do not fit with any known layered silicate [1–5]. Many similarities were found to hydrous alkali silicates (metal silicate hydrates, M-SH-type).The new silicate differs from M-SH by a high structural stability, against a wide range of different energetic influences. Due to the relatively high stability, high-resolution electron microscopy (HREM) can be applied to study the layer structure of this silicate as a representative of the M-SH silicates. All known M-SH, for example, magadiite and kenyaite are decomposed by the electronic beam. 相似文献
Non-covalent interactions play an essential role in directing the self-assembly of hybrid organic–inorganic crystals. In hybrid halide perovskites, hydrogen bonding has been the paramount non-covalent interaction. Here, we show another non-covalent interaction, namely, the halogen bond interaction, that directs a symmetry-breaking assembly in a new series of two-dimensional (2D) perovskites (ICH2CH2NH3)2(CH3NH3)n−1PbnI3n+1 (n is the layer thickness, n=1–4). Structural analysis shows that the halogen bond strength varies with the layer thickness. For the odd number (n=1, 3) layered perovskites, stronger halogen interaction leads to centrosymmetric structures, whereas for the n=2 layered perovskites, weaker halogen bonds result in non-centrosymmetric structures. Transient reflection spectroscopy shows a suppressed radiative recombination rate (k2≈0) and prolonged spin lifetime for n=2 structure, suggesting an enhanced Rashba band splitting effect. The structural asymmetry is further confirmed with a reversible bulk photovoltaic effect. Our work provides a new design strategy to enable hybrid perovskites with emerging properties and functionalities associated with structural asymmetry. 相似文献
A novel isopropanol-pyrogallol[4]arene forms a layered structure via hydrogen bonding and C–H…π interactions. The layered structure results in encapsulation of one isopropanol molecule. The application of NMR methods to determine solution structures and crystal structures provides insight into host–guest properties and the molecular interactions between them. 相似文献
Two types of layered hydroxide zinc m‐aminobenzoate compounds with structures of layered basic metal salt (LBMS) were prepared by the reaction of zinc hydroxide with m‐aminobenzoic acid solution in the temperature range of 40–120°C. The formation reactions, structures, chemical compositions, and exfoliation reactions of the layered compounds in alcohol solvents were investigated by XRD, TG‐DTA, SEM, and TEM. One layered phase with a basal spacing of 1.08 nm has a α‐Ni(OH)2‐like structure, and its chemical formula can be written as Zn(OH)0.67(m‐NH2C6H4COO)1.33. This phase has strip‐like particle morphology and cannot be exfoliated into its nanosheets in alcohol solvents. The other layered phase with a basal spacing of 2.66 nm has a zinc hydroxide‐nitrate‐like structure, and can be exfoliated in alcohol solvents. 相似文献
Micellar structures of amphiphilic poly(1,2‐butadiene)‐block‐poly(ethylene oxide) diblock copolymers have been crosslinked in aqueous solution by γ‐irradiation. By transmission electron microscopy (TEM) of negatively stained specimens it is shown that the predominant structures present are copolymer vesicles (which appear to be double‐layered). These fixed vesicles are stable with respect to their shape and can be transferred from water into a good solvent for both blocks, such as tetrahydrofuran, thus demonstrating the effectiveness of the crosslinking. In addition to the vesicles, a small number of flexible cylindrical/filamentous structures, sequentially fused vesicles/strings of vesicles and giant sheet‐like vesicles are also visible after cross‐linking. The vesicle chains seem to be formed by fusion of the double‐layered vesicles; the outer layer of the vesicles apparently fuses sequentially, whereas the inner shell remains intact, creating periodic linear thickenings. 相似文献
Based on FLAPW-GGA calculations, a comparative study of the features of interatomic interactions in LaFeAsO, SrFe2As2, and LiFeAs layered crystals (basic phases of new 18–56 K superconductors) is carried out.
Original Russian Text Copyright ? 2009 by I. R. Shein and A. L. Ivanovskii
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Translated from Zhurnal Strukturnoi Khimii, Vol. 50, No. 3, pp. 573–576, May–June, 2009. 相似文献