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Measurements of nonlinear microwave losses in doubble-sided YBCO and GBCO films are examined and reported.

A much simplified template, such as two nonsuperconducting layers between the superconducting Y[Ba.sub.2][Cu.sub.3][O.sub.7-[delta]] (YBCO) and the polycrystalline metal substrate, is developed for high-performance coated conductors by using biaxially aligned TiN as a seed layer. The YBCO films grown on electropolished polycrystalline Hastelloy using the two-layer template has displayed a superconducting transition temperature, a critical current density and an [alpha] value, indicating a high density of pinning centers and an absence of weak links.

The article employs the different thin film sees to analyze the multiseeded melt growth of bulk Y-Ba-Cu-O compounds. An increase in the grain boundary contact angle is shown to lead to a significant decrease in the extent of residual melt deposited at the grain boundary.

Abstract: Vanadium carbide (V8C7) nanopowders were prepared through simultaneous thermal decomposition and carbothermal reduction of the precursor VOC2O4/sucrose in vacuum. The products were characterized by X-ray diffractometer (XRD) and transmission electron microscopy (TEM) techniques. The thermolysis process of the precursor has been investigated by themogravimetric analysis and differential thermal analysis (TG-DSC). The results showed that the pure V8C7 powders can be obtained at 950°C for 30min and the particle size is in the range from 30 to 50nm with good dispersion. The effects of experimental parameters and reaction mechanism have been explored. The lower synthesis temperature and shorter reaction time were attributed to take the quadrivalence vanadium as a reactant, as well as carbon source and vanadium source intimate contact in the precursor. This facile and quickly synthetic strategy may open a new route to the preparation of other carbide nanomaterials. [Copyright &y& Elsevier]

Abstract: YBa2Cu3O7−δ (YBCO) films were prepared on single-crystal SrTiO3 substrates with metal–organic deposition using trifluoroacetates (TFA-MOD). Positive results have been acquired in controlled study to investigate the effects of substrate surface modification on the growth-induced flux-pinning nanostructures in YBCO films. Nanoscale CeO2 particles were applied to single-crystal SrTiO3 substrate surfaces using pulsed laser deposition before YBCO precursors coating. Superconducting properties of the YBCO films grown on the controlled CeO2-modified substrates have shown substantial improvement in the critical current densities (J c) at 77K over those grown on untreated substrates in almost all the field (78% increment at 1T,77K). We think the reason is that the CeO2 nanoparticles act as pinning centers. [Copyright &y& Elsevier]

Abstract: Ba0.65Sr0.35TiO3 (BST) thin films were deposited by RF sputtering with a very thin Ba0.65Sr0.35RuO3 (BSR) seeding-layer on Pt/Ti/SiO2/Si substrate. The crystallization of BST thin films and the surface morphology of BSR seeding-layer were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. XRD patterns show that the BSR seeding-layer affected the orientation of BST thin film, which is highly a-axis textured. It was also found that the BSR seeding-layer had a marked influence on the dielectric properties of BST thin films. Comparing with BST thin films directly deposited on Pt electrode, the dielectric relaxation can be suppressed and dielectric constant increased due to a possible reduction of interface oxygen vacancies at BST/BSR interface. Moreover, J–V measurement indicates that the leakage current density of BST thin films on BSR seeding-layer were greatly reduced compared with that of BST thin films directly on Pt electrodes. The pyroelectric coefficient of BST thin films with BSR seeding-layer is 7.57×10−7 Ccm−2 K−1 at 6V/μm at room temperature (RT). Our results reveal that high pyroelectric property of BST thin film could be achievable using BSR seeding-layer as a special buffer. [Copyright &y& Elsevier]