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Interferometric thermal diffusivity measurements and elastic constants obtained by ultrasonic techniques on YFeAlO (with ϰ 4 0, 0.4, 0.8, 1.1) ceramic samples are presented and discussed. The phonon mean free path is given as a function of ϰ using the Boltzmann transport equation. [ABSTRACT FROM AUTHOR]

Samarium element has been substituted to yttrium in Y123 superconducting melt textured bulk samples in order to make the whole fabrication process much faster. A preliminary comparison between directionally solidified YBaCuO and SmBaCuO bulk bars fabricated with the horizontal Bridgman method has been done. The different microstructural and superconducting features are studied by means of X-ray, SEM analysis, ac and dc susceptibility measurements. The quality of Sm123 samples appears comparable with the Y123 one grown using an almost two orders of magnitude lower pulling rate. [ABSTRACT FROM AUTHOR]

Because of their intrinsic layered structure, high temperature superconductors are suitable systems for studying the strong anisotropy of their superconducting properties. In fact, the response of a sample to an external magnetic field H depends generally not only on the magnitude but also on the orientation of H. Since remanent magnetization is a measurement of the effective flux-pinning strength in superconductors, it depends upon both the temperature and the applied field, as well as on the history of processing and the angle between the applied magnetic field and the crystallographic axis directions. In this framework we report the studies of the angular dependence of remanent isothermal magnetization M in YBCO sputtered films. The projections of the remanent magnetization on the direction of the magnetometer axis were measured for each of the films. The results show the orientational preference for flux trapping, related to intrinsic features. Moreover, an angular dependence of the remanent magnetization can be calculated in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Ag/BSCCO-2223 phase tapes were prepared with a new plastic deformation cycle. Starting from the hot extrusion of composite billets, hundreds of metres of tape 0.15×3 mm were obtained by drawing and rolling the extruded bars. The cross-section, monofilamentary with a central Ag insert, is quite regular along all the length. Samples from 30 cm to 100 cm in length were heat-treated at different temperatures between 830°C and 480°C in Ar+10% O atmosphere. Electrical-transport properties were tested at 77K. J of 3000 A/cm were usually achieved after first heat treatment. The superconducting properties were also tested by magnetic measurements using a vibrating sample magnetometer. [ABSTRACT FROM AUTHOR]

Epitaxial films of YBaCuO were deposited in situ on LaAlO substrates using single-target 90° off-axis sputtering. The films were characterized by magnetization measurements ( M vs. T, H), applying the field parallel to c-axis. The observed differences in the T and J values are attributed to the different oxygen content in the superconducting films. [ABSTRACT FROM AUTHOR]

Superconducting films of YBaCuO were deposited in situ on LaAlO substrates using single-target 90° off-axis sputtering. The obtained films have tipical T values of 91K. Surface resistance measurements on as-grown films reach 1.1 mΩ at 77K and 10GHz; whilst on ion-etched patterned resonant lines R (77K, 10GHz) it is about 10mΩ. [ABSTRACT FROM AUTHOR]

BSCCO (2223) phase superconductor, prepared by the traditional solid-state reaction route, was densified by hot pressing, yielding high-density and textured-bulk materials. A correlation between processing parameters and inter-, intra-granular properties of the sample was performed through the evaluation of microstructural features and the study of electrical resistivity and magnetization behaviour as a function of different temperature and magnetic field. [ABSTRACT FROM AUTHOR]

Polycrystalline YBCO was prepared by a pyrolytic process starting from citrate and tartrate precursors. The effect of the precursor on the superconducting properties was investigated by means of magnetic measurements using a SQUID magnetometer, a Vibrating-Sample Magnetometer and an a.c. susceptometer. The critical temperature is not affected by the type of precursor ( T =85 K for both). On the other hand, the precursor plays an important role on the critical current density, which is found to be an order of magnitude higher in the sample obtained from citrates ( J (77K, H=0)=2.3·10 A/cm and 10 A/cm for the from-citrate and from-tartrate sample, respectively). [ABSTRACT FROM AUTHOR]