E. Hannachi

Fluctuation induced magneto-conductivity of Y3Ba5Cu8O18±x and YBa2Cu3O7−d

A comparative study of the fluctuation magneto-conductivity in YBa2Cu3O7−d (noted Y-123) and Y3Ba5Cu8O18±x (noted Y-358) polycrystalline samples was carried out. Samples were synthesized in oxygen atmosphere using a standard solid state reaction technique. Phases and microstructure have been systematically investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The magneto-conductivity was measured in a magnetic field ranging from 0 T to 7 T applied perpendicular to the current path direction. The magneto-conductivity data were analyzed in terms of the temperature derivative of the resistivity and the logarithmic temperature derivative of the conductivity χσ = −d(ln Δσ) dT, where Δσ is the fluctuation conductivity. Analyses of the magneto-conductivity data reveal that Y-123 possesses a better quality of intrinsic Josephson junction compared to Y-358 one while in the former one the depression in superconducting temperature is more pronounced. The applied magnetic field narrowed substantially the three dimensions (3D) Gaussian regime and for Y-358 sample this regime is vanished for high magnetic field ( >1 T). Results are discussed in relation with the difference in the structure and microstructure Y-358 and Y-123. The upper critical and the irreversibility magnetic fields were estimated and were found to be higher in the Y-358 sample.

Effect of nanowires SiO2 on superconducting properties of YBa2Cu3O7−d bulks

The effects of SiO2 nanowires on the superconducting properties of YBa2Cu3O7−d (YBCO) compound were studied. Samples were synthesized in air using a standard solid state reaction technique by adding nanowires SiO2 up to 1wt.%. Phase analysis by X-ray diffraction (XRD), microstructure investigation by scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDXS), critical current density dependence on applied magnetic field Jc(H) and electrical resistivity as a function of temperature ρ(T) were carried out to evaluate the relative performance of samples. We find that Tco does not change much (90.8-90.2 K) with the low concentration of SiO2 (≤ 0.1 wt.%) and Jc(H) is enhanced.

Effect of nanowires SiO{sub 2} on superconducting properties of YBa{sub 2}Cu{sub 3}O{sub 7−d} bulks

The effects of SiO2 nanowires on the superconducting properties of YBa2Cu3O7−d (YBCO) compound were studied. Samples were synthesized in air using a standard solid state reaction technique by adding nanowires SiO2 up to 1wt.%. Phase analysis by X-ray diffraction (XRD), microstructure investigation by scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDXS), critical current density dependence on applied magnetic field Jc(H) and electrical resistivity as a function of temperature ρ(T) were carried out to evaluate the relative performance of samples. We find that Tco does not change much (90.8-90.2 K) with the low concentration of SiO2 (≤ 0.1 wt.%) and Jc(H) is enhanced.

Effect of nanowires SiO2on superconducting properties of YBa2Cu3O7−dbulks

The effects of SiO2 nanowires on the superconducting properties of YBa2Cu3O7−d (YBCO) compound were studied. Samples were synthesized in air using a standard solid state reaction technique by adding nanowires SiO2 up to 1wt.%. Phase analysis by X-ray diffraction (XRD), microstructure investigation by scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDXS), critical current density dependence on applied magnetic field Jc(H) and electrical resistivity as a function of temperature ρ(T) were carried out to evaluate the relative performance of samples. We find that Tco does not change much (90.8-90.2 K) with the low concentration of SiO2 (≤ 0.1 wt.%) and Jc(H) is enhanced.

The normal state properties of nano-sized CoFe{sub 2}O{sub 4} added Bi-based superconductors in bipolaron model

The effect of nano-sized CoFe2O4 particles (10 nm in diameter) addition on the structure and the normal state transport properties of polycrystalline Bi-based superconductors were systematically studied. The additional amount, x wt.%, of CoFe2O4 in this case varied from 0.0 to 1 wt.% of the total mass of the sample. Phase analysis by X-ray diffraction (XRD) and Electrical resistance as a function of temperature, ρ(T) were carried out. Nano-sized particles addition modifies the electrical behavior of the normal state with increasing the CoFe2O4 concentration. The bipolaron model can explain properly the normal state resistivity of the samples.