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High-entropy single-phase superconducting oxide Y0.2Nd0.2Eu0.2Sm0.2Ho0.2Ba2Cu3Oy was synthesized. For samples with different values of oxygen content thermogravimetry, x-ray diffraction and magnetic properties were measured. Orthorombitity, critical temperature, and critical current grow with oxygen nonstoichiometry value y and corresponds to those for "low-entropy" YBa2Cu3Oy-type superconductors. The increase of the oxygen content leads to a decrease of "buckling" CuO2 layers and does not lead to a decrease in the Ba–O distance. [ABSTRACT FROM AUTHOR]

Incorporating different anions with varied ionic sizes and charges is a rapidly growing approach to bring out unusual physical properties among various classes of solid-state materials, pnictides and chalcogenides in particular. This minireview is focused on hetero-anionic materials based on the pnictogens, which have been demonstrated to offer an impressive diversity of crystal chemistry and electronic structures. In addition, many pnictide oxides or oxypnictides, over the course of the last decade, have been shown to exhibit a broad spectrum of superconducting, magnetic, and semiconducting properties. However, the structural diversity of the mixed-anion materials is far greater than the several known structure types, or their variants, of the well-known layered superconductive materials. Therefore, with this treatise, we aim to provide a comprehensive overview of the crystal chemistry of pnictide oxides by recounting almost 40 different structures of such ternary and multinary compounds. In addition to the structural aspects, we also highlight some of the challenges associated with the synthesis, and briefly summarize reported, to date, physical properties of this remarkable class of solids. [ABSTRACT FROM AUTHOR]

Bi1.6Pb0.4Sr2Ca2Cu3Oy superconductor samples doped with graphene oxide (GO) in different weight percentages (0 wt.%, 0.002 wt.%, 0.004 wt.%, and 0.010 wt.%) were synthesized by a solid-state reaction method and then characterized. The structure and morphology of the samples were characterized by x-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). XRD analysis revealed that all the samples contained Bi-2223 and Bi-2212 phases with a small amount of impurity phase. The results showed that GO doping did not change the lattice parameters or structure of the samples dramatically, indicating that GO remains between the grains, playing a role of weak links. SEM revealed that all the samples had randomly distributed grains with plate-like shape. A decrease of the pore size, and hence enhanced densification and better connections between the grains, was observed for the 0.010 wt.% GO-doped sample when compared with the other samples. Magnetization measurements (M–T) were used to determine the onset critical temperature (Tc) of each sample, revealing that Tc decreased with increasing GO content up to x = 0.004 but increased slightly for the GO content x = 0.010. The results also showed that the highest onset critical temperature, Tc (75 K) and Josephson current, I0 (5.89 µA) values were obtained for the 0.010 wt.% GO-doped sample, which thus represents the optimum doping amount to improve the magnetic and structural properties. [ABSTRACT FROM AUTHOR]

Several precursor powders, obtained after precipitation from metal nitrate solution containing polyethylene glycol (PEG) (inside a Pyrex glass reactor or by spray‐drying), and their thermal evolution to GdBa2Cu3O6+x (GdBCO) were analyzed by thermogravimetry, differential thermal analysis, Fourier‐transform infrared spectroscopy, and X‐ray diffraction. The amount of PEG had a crucial role in the BaCO3 content of the "Kjeldahl precursors," but a minor effect on the degree of transformation to GdBCO at 900°C, which did not reach completion after 1 hour. In contrast, a low‐PEG spray‐dried powder led to almost 100% GdBCO in only 5 minutes. The high degree of cation dispersion reached by spray‐drying and the coexistence with a liquid phase can explain this short reaction time. The spray‐dried powder compares favorably with the mechanical mix of metal oxides and Ba carbonate that is commonly used as precursor powder for the synthesis following a solid‐state reaction. [ABSTRACT FROM AUTHOR]

The heteroepitaxial growth of Re (0001) films on Nb (110) surfaces has been investigated. Nb/Re bilayers were grown on A-plane sapphire-α-Al2O3 (1120)-by molecular beam epitaxy. While Re grew with a (0001) surface, the in-plane epitaxial relationship with the underlying Nb could be best described as a combination of Kurdjumov-Sachs and Nishiyama-Wassermann orientations. This relationship was true regardless of Re film thickness. However, an evolution of the surface morphology with increasing Re thickness was observed, indicative of a Stranski-Krastanov growth mode. Re (0001) layers less than 150 Å thick were atomically smooth, with a typical rms roughness of less than 5 Å, while thicker films showed granular surface structures. And despite the presence of a substantial lattice misfit, the Re layer strain diminished rapidly and the Re lattice was fully relaxed by about 200 Å. The strain-free and atomically smooth surface of thin Re overlayers on Nb is ideal for the subsequent epitaxial growth of ultra-thin oxide tunnel barriers. Utilizing bcc/hcp (or bcc/fcc) heteroepitaxial pairs in advanced multilayer stacks may enable the growth of all-epitaxial superconductor/insulator/superconductor trilayers for Josephson junction-based devices and circuits. [ABSTRACT FROM AUTHOR]

A series of quasimultilayers consisting of YBa2Cu3O7-δ (YBCO) and SrRuO3 (SRO), namely, p×(YBCO(m)/SRO(n)) (p: repetition periods; m: YBCO pulse number; n: SRO pulse number), is prepared on single crystal SrTiO3 by pulsed laser deposition. X-ray diffraction measurements reveal that a heterogeneous phase of Ba2YRuO6 is formed due to the chemical reaction, while both the in-plane and out-of-plane textures of the present quasimultilayers are as good as in the pure YBCO films. The content of Ba2YRuO6 increases as the pulse number of SRO increases, leading to the decrease in superconducting transition temperature (Tc). There is no obvious difference in Tc between the samples with the different deposition sequence orders of YBCO and SRO. The magnetic field dependence of critical current density (Jc) shows an enhanced flux pinning at relatively high fields for all the present quasimultilayers, which occurs at different ranges of fields depending on the applied temperatures. The Jc of the quasimultilayers can reach two times higher than that of pure YBCO films in a wide range of magnetic fields, which shows the promising application for coated conductors. [ABSTRACT FROM AUTHOR]