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We report a rare experimental evidence of an exceptional increase in grain-boundary diffusion-controlled growth kinetics of product phase by grain-refinement due to minor alloying. Ti-addition during growth of V 3 Ga superconductor by coupling V and Cu(Ga)-solid solution by bronze process increases the critical current density ( J c ) significantly. In this manuscript, the exact role of Ti-addition is studied based on systematic and quantitative diffusion-couple experiments that mimic the bronze-method. Metallurgical aspects like microstructural features and growth mechanism are assessed critically. Results are compared when Ti is added either to V or Cu(Ga) and to both for a fixed Ga content. Ti-addition to Cu(Ga) compared to V increases growth kinetics of V 3 Ga more significantly. Quantitative EPMA-analysis indicates that a mixture of Ti-free and Ti-containing V 3 Ga phase grows when Ti is added to V. Small precipitates grow along with Ti-containing V 3 Ga when Ti is added only to Cu(Ga). TEM-study indicates that these precipitates are rich in V and Ti. Much finer grains found in the precipitate-containing region lead to higher growth kinetics due to grain-boundary diffusion. EBSD-analysis shows equiaxed grains and relatively random in orientation because of alloying. This study indicates that Ti-addition to Cu(Ga) is most effective considering metallurgical aspects that influence J c . [ABSTRACT FROM AUTHOR]

Abstract: In this study, the mechanical properties of YBa2Cu3O7−x , obtained by the Bridgman technique, were examined using a Berkovich tip indenter on the basal plane (001). Intrinsic hardness was measured by nanoindentation tests and corrected using the Nix and Gao model for this material. Furthermore, Vickers hardness tests were performed, in order to determine the possible size effect on these measurements. The results showed an underestimation of the hardness value when the tests were performed with large loads. Moreover, the elastic modulus of the Bridgman samples was 128±5GPa. Different residual imprints were visualised by atomic force microscopy and a focused ion beam, in order to observe superficial and internal fracturing. Mechanical properties presented a considerable reduction at the interface. This effect could be attributed to internal stress generated during the texturing process. In order to corroborate this hypothesis, an observation using transmission electron microscopy was performed. [Copyright &y& Elsevier]

The different steps of a cryogenic low-noise amplifier design are presented. The noise parameters of a HEMT transistor are measured and used to determinate the Pospieszalski noise model 1. This noise model is used for the design of a one-stage LNA for which the matching circuits are realised with superconductor material for optimal noise performances. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 242–245, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11341 [ABSTRACT FROM AUTHOR]

The present study exhibits design and analysis of a superconductor-based defective 1D photonic crystal (PhC) to envisage an ultra-high sensitive ethanol sensor. The proposed structure is realized with alternate layers of high temperature superconductor (YBa 2 Cu 3 O 7) and dielectric (SrF 2) material, whereas the central defect layer is designed with porous silicon (P-Si) material. Transmittance and absorption spectrum are explored theoretically by employing transfer matrix method and two-fluid model. The mainstay of this work is to investigate the shift in wavelength of the resonant mode, which is created within the band gap, in the transmittance spectrum. The position of the defect mode wavelength is assayed by varying the incidence angle, thickness of superconductor layer and operating temperature. An ultra-high wavelength sensitivity of 8.53 × 10 5 nm/RIU and temperature sensitivity of 6.673 nm/K are achieved by the proposed sensor, which open up an avenue for effective sensing of different % volume of ethanol with minute refractive index contrast. Besides sensitivity, other sensing parameters like figure of merit, quality factor and detection limit are thoroughly studied and compared with the recently published works. On top of that, the simple structure, easy analysis, and available fabrication techniques make the proposed design a suitable candidate for biosensing applications. [ABSTRACT FROM AUTHOR]