Single crystal

About: Single crystal is a research topic. Over the lifetime, 59617 publications have been published within this topic receiving 870828 citations.

Highly stable chiral cadmium 1,2,4-benzenetricarboxylate: synthesis, structure, and NLO and fluorescence properties.

Abstract: Employing an unsymmetrical 1,2,4-benzenetricarboxylate as a bridging ligand, a new 3-D chiral cadmium coordination polymer [Cd2(OH)(1,2,4-BTC)] (1,2,4-BTC = 1,2,4-benzenetricarboxylate) has been prepared under hydrothermal conditions and characterized by single crystal X-ray diffraction. This compound crystallizes in the orthorhombic space group P212121, with cell parameters a = 6.900(2) A, b = 7.404(3) A, c = 19.116(5) A, V = 976.5(5) A3, and Z = 4. Its structure contains 2-D Cd−O−Cd connectivity, which is further linked by the 1,2,4-BTC ligand into a 3-D supramolecular framework. The 1,2,4-BTC ligand shows a novel and unprecedented coordination mode: nine bonds to eight metals with each carboxylate as a tridentate group. The compound exhibits intense photoluminescence at room temperature and shows distinct NLO properties. On the basis of the results of TG/DTA analyses, the structure is thermally stable up to ∼ 380 °C.

Atom-resolved imaging of ordered defect superstructures at individual grain boundaries

Abstract: The ability to resolve spatially and identify chemically atoms in defects would greatly advance our understanding of the correlation between structure and property in materials. This is particularly important in polycrystalline materials, in which the grain boundaries have profound implications for the properties and applications of the final material. However, such atomic resolution is still extremely difficult to achieve, partly because grain boundaries are effective sinks for atomic defects and impurities, which may drive structural transformation of grain boundaries and consequently modify material properties. Regardless of the origin of these sinks, the interplay between defects and grain boundaries complicates our efforts to pinpoint the exact sites and chemistries of the entities present in the defective regions, thereby limiting our understanding of how specific defects mediate property changes. Here we show that the combination of advanced electron microscopy, spectroscopy and first-principles calculations can provide three-dimensional images of complex, multicomponent grain boundaries with both atomic resolution and chemical sensitivity. The high resolution of these techniques allows us to demonstrate that even for magnesium oxide, which has a simple rock-salt structure, grain boundaries can accommodate complex ordered defect superstructures that induce significant electron trapping in the bandgap of the oxide. These results offer insights into interactions between defects and grain boundaries in ceramics and demonstrate that atomic-scale analysis of complex multicomponent structures in materials is now becoming possible.

Superconducting properties and crystal structures of single‐crystal niobium nitride thin films deposited at ambient substrate temperature

Abstract: Single‐crystal niobium nitride (NbN) thin films were fabricated at ambient substrate temperature so that photoresist lift‐off techniques could be used in fabricating Josephson tunnel junctions In this article, we describe the superconducting properties and crystal structure of the NbN films Even though the substrates were not heated, the NbN films had excellent superconducting properties: a high Tc of 16 K, low normal‐state resistivity (ρ20=62 μΩ cm), and residual resistivity ratios RRR=ρ300/ρ20 above one The film structures, which were investigated by x‐ray diffraction, electron diffraction patterns and transmission electron micrographs, show a single‐phase orientation without columnar and granular structures We have found that the superconducting properties depend on the lattice parameter, and the best films had a lattice parameter of 0446 nm NbN/AlN/Nb tunnel junctions were fabricated to measure the superconducting energy gap of the NbN films We estimated the energy gap ΔNbN to be 26 meV and th

Direct measurement of the temperature-dependent magnetic penetration depth in Y-Ba-Cu-O crystals.

Abstract: The temperature dependence of the magnetic penetration depth lambda is determined directly from low-field dc magnetization measurements on single crystal Y-Ba-Cu-O (T/sub c/ = 89.7 K, ..delta..T/sub c/ = 0.2 K). The results are consistent with the behavior expected from a BCS (s wave) superconductor.

Abnormal Grain Growth Induced by Cyclic Heat Treatment

Abstract: In polycrystalline materials, grain growth occurs at elevated temperatures to reduce the total area of grain boundaries with high energy. The grain growth rate usually slows down with annealing time, making it hard to obtain grains larger than a millimeter in size. We report a crystal growth method that employs only a cyclic heat treatment to obtain a single crystal of more than several centimeters in a copper-based shape-memory alloy. This abnormal grain growth phenomenon results from the formation of a subgrain structure introduced through phase transformation. These findings provide a method of fabricating a single-crystal or large-grain structure important for shape-memory properties, magnetic properties, and creep properties, among others.