The effect of Ag doping concentration on the microstructure, transport properties and weak-link profile of YBa 2 Cu 32x -Ag x O 72d bulk superconducting compound was investigated through resistance -temperature ðR-TÞ; ac magnetic susceptibility ðx 2 TÞ; scanning electron microscope (SEM), X-ray diffraction (XRD) and the critical current density ðJ c Þ versus applied magnetic field ðJ c 2 BÞ measurements. We used the additive method with cationic ratio of x ¼ 0:1 2 0:4 for the YBCO-Ag system. The change in the silver doping concentration slightly affected the transition temperatures ðT c;zero Þ; whereas, the critical current densities ðJ c Þ of the samples and their magnetic field ðBÞ dependencies were noticeably affected. The improvement on the microstructural properties of YBCO bulk superconductors was observed in SEM analysis, the J c values increased and their magnetic field dependencies decreased with the increasing of Ag concentration up to x ¼ 0:2: As well as the current transport properties. Ag doping up to a certain amount produces texturing that gives rise to a modification in the weak-link profile resulting in an enhanced strength of flux pinning which causes an increase in the current carrying capacity. q

Dependence of the phase and magnitude of the response of MgO substrate YBa 2 Cu 3 O 7Àd (YBCO) transition edge bolometers to the near infrared radiation on the superconducting transition width is presented in this work. The bolometers were made of YBCO thin films of 200 nm thickness that were grown on single crystal MgO (1 0 0) substrates by DC inverted cylindrical magnetron sputtering. We have measured the responses of both large and small area devices with respect to the bias temperature and radiation modulation frequency. We have observed that the superconducting transition width has major effects on the response of the bolometers such as; on a dip of the phase of the response versus modulation frequency curve around 1 Hz, the rate of decrease of the magnitude of the response, and dependence of the phase of the response on temperature at mid-range modulation frequency. We have investigated a correlation between the superconducting transition width and the YBCO film surface morphology of the devices. In addition, the illumination wavelength dependence of the optical response of both wide and narrow transition width devices has been investigated. Here we present the analysis and the possible mechanisms that can affect the response of the bolometers at the superconducting transition region.

The dependence of YBCO thin film properties on the deposition conditions was studied for different substrates. The deposition conditions were optimized for the epitaxial growth of high quality YBCO thin films of 1500 Å thickness onto single crystal (100-oriented) SrTiO 3 (STO), MgO and LaAlO 3 (LAO) substrates by DC Inverted Cylindrical Magnetron Sputtering (ICMS). The samples were investigated in detail by means of X-ray diffraction analysis (XRD), EDX, AFM, r -T; magnetic susceptibility and current -voltage ðI -VÞ characterizations. The samples show strong diamagnetic behavior and sharp transition temperatures of 89 -91 K with DT , 0:5 K. XRD of the samples exhibited highly c-axis orientation. The full width at half maximum (FWHM) values of the rocking curves were ranging typically from 0.22 to 0.288. The samples have smooth surfaces as shown from AFM micrographs. The surface roughness, R a , changed between 5 -7 nm. I -V characteristics were obtained from the 20 mm-wide microbridges, which were patterned by a laser writing technique. The critical current densities (J c ; 1.06 £ 10 6 for LAO-based YBCO, 1.39 £ 10 6 for MgO-based YBCO, 1.67 £ 10 6 A/cm 2 for STO based YBCO) of the microbridges were evaluated from I -V curves at 77 K. q

a b s t r a c tThe effects of post-annealing temperature were investigated on Bi 2 Sr 2 Ca 1 Cu 2 O 8+o thin films deposited on MgO (1 0 0) substrates by pulsed laser deposition (PLD). The structural and superconducting properties of the films have been determined by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature depende nt resistivity (R-T), and DC magnetization measure ments. The films which were deposited at 600 °C were post-annealed in an atmosphere of a gas mixture of Ar (93%) and O 2 (7%), at temperature ranging between 800 and 880 °C. This resulted in films which exhibited a single phase of 2212 with a high crystallini ty (FWHM % 0.16°) and texturing along the c-axis, perpendicular to the plane of the substrate. An optimum temperature of 860 °C was found for the post-annealing thermal treatment. The critical temperature, T C , of the films was measure d as 82 K and the critical current density, J C , was calcu lated as 3 Â 10 7 A/cm 2 for the film annealed at 860 °C.

Bi 2 Sr 2 Ca 1 Cu 2 O 8 þ ∂ thin films were deposited on MgO (100) substrates by pulsed laser deposition (PLD). The effects of post-annealing time on the phase formation, the structural and superconducting properties of the films have been investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature dependent resistivity (R-T), atomic force microscopy (AFM), and DC magnetization measurements. The films deposited at 600 1C were post-annealed in an atmosphere of a gas mixture of Ar (93%) and O 2 (7%), at 860 1C for 10, 30, and 60 min. All films have demonstrated a mainly single phase of 2212 with a high crystallinity (FWHM E 0.1591) and c-axis oriented. The critical temperature, T C , of the films annealed for 10, 30, and 60 min were obtained as 77, 78, and 78 K, respectively. The highest critical current density, J C , was calculated as 3.34 Â 10 7 A/cm 2 for the film annealed at 860 1C for 30 min at 10 K.