Saçılma yöntemi ile üretilen Bi(Pb)SrCaCuO süperiletken ince filmin elektiriksel ve magnetik özellikleri

The main objective of this thesis is to not only determine the optimum annealing ambient for the Bi(Pb)SrCaCuO superconductor thin film production but investigate the electrical, physical, microstructural, pinning mechanism and superconducting properties of the thin films produced by sputtering method at 100 watt DC power by means of scanning electron microscopy (SEM), X-Ray diffraction analysis (XRD), electron dispersive X-Ray (EDX), resistivity and transport critical current density measurements for applications in technology and industry, as well. In the first stage, after the literature research, we determined the various annealing time (15 min, 1.5 h and 3 h) and temperature (850, 860 and 870 °C) to produce the Bi(Pb)SrCaCuO film obtaining the best surface morphology and superconducting properties. The measurements given above are carried out on the 9 films produced. Experimental results obtained show that the superconductor film annealed at 860 ? C for 3 h exhibits the greatest Bi-2223 phase fraction, highest critical temperature, critical current density, best texturing, crystallinity and connectivity between grains, largest grain size and lowest porosity. In the second stage, the pinning mechanism and superconducting properties of the Bi-2223 thin film annealed at 860 °C for 3 h are analyzed with the aid of the magnetoresistivity measurements conducted at several applied magnetic fields in a range of 0-3 T as a function of temperature changing from 20 to 130 K. The onset ( ) and offset ( ) critical temperatures, variation of the critical temperature, activation energy (U0), irreversibility field (?0Hirr), upper critical field (?0Hc2), penetration depth (?) and coherence length (?) of the film are evaluated from the magnetoresistivity curves. It is found that the superconducting properties degrade with the increment in the applied magnetic field as a result of the weak links between the superconducting grains in the sample. In the last stage, atomic force microscopy (AFM), magnetoresistivity and transport critical current density measurements as a function of the magnetic field direction (dc magnetic field and the angle between the surface of the film and the applied magnetic field) are performed to examine the anisotropic nature of the Bi-2223 film produced. The field direction to the film surface is changed from 0° to 90° by 15° steps. Moreover, activation (pinning) energy values of the film studied are found using thermally activated flux creep model when flux pinning force is analyzed by Kramer equation. It is found that the superconducting properties of the Bi-2223 superconducting film, the surface of which is centrally distributed and comprised of disproportionate number of peaks, decrease systematically with the increment of both the applied magnetic field and the angle up to 90° (?0H//c-axis). To sum up, the pinning mechanism and superconducting properties are strongly dependent upon both the applied magnetic field and the angle ( ? ), presenting the anisotropic character of the sample produced.Keywords: Bi-2223 superconductor thin film, Annealing ambient, Critical temperature, Critical current density, Activation energy, Pinning mechanism, Anisotropic behavior