الفهرس 
History of superconductivityOnly 14 pages are availabe for public view
 |  | from | 203 |  |  |
| | | from | 203 | | |
Abstract
The superconductor YBa2Cu3O7-δ (Y123) and Y3Ba5Cu8O18-δ (Y358) is
prepared by the solid-state route, while the nanosized Ni0.5Zn0.5Fe2O4 (Ni-Zn
ferrite) is synthesized via citric acid sol-gel technique. The superconducting
materials doped with different ratios (0.00, 0.01, 0.03, 0.05, 0.10, and 0.50 wt%)
of nanosized Ni0.5Zn0.5Fe2O4 are prepared by a modified solid-state method, to
study the effect of doping Ni-Zn nanosized ferrite on the superconducting,
structure, and thermal properties of Y123 and Y358. The prepared samples show
Meissner effect which confirmed the presence of superconducting phase at
liquid nitrogen temperature (77 K). The prepared samples have been
characterized by X-ray diffraction (XRD), Transmission Electron Microscopy
(TEM), scanning electron microscopy (SEM), energy dispersion of X-ray
(EDX), infra-red (IR) spectroscopy, thermogravimetric analysis (TGA),
vibrating sample magnetometer (VSM), DC resistance by four-probe, and
critical current density measurements.
1- For the first series (Ni0.5Zn0.5Fe2O4)x /YBa2Cu3O7-δ:
It was found that by increasing Ni0.5Zn0.5Fe2O4 nanoparticles in the Y123
compound, the unit cell volume of the orthorhombic phase decreases, but the
transition temperature Tc and critical current density Jc decrease for low doping
(x = 0.03 wt%) then increase for (x = 0.10 and 0.50 wt%) Ni0.5Zn0.5Fe2O4 doped
in Y123. The transport properties of the (Ni0.5Zn0.5Fe2O4)x/YBa2Cu3O7-δ
composite as electrical resistance R, Tc, and Jc are interpreted according to
Bean’s critical state model and charge-vortex interaction combined with vortex
pinning in Y123 high-Tc mixed-state type-II superconductor.
Abstract
vii
2- For the second series (Ni0.5Zn0.5Fe2O4)x /Y3Ba5Cu8O18-δ:
It was found that by increasing Ni0.5Zn0.5Fe2O4 nanoparticles into Y358
compound, the unit cell has lattice constants for pure Y358 (a = 3.9557Å,
b = 3.8197Å, and c = 30.2460Å). The maximum values of the transition
temperatures are attained for sample doped with x = 0.01wt% has Tc
on = 105K,
Tc
mid = 95K, and Tc
off = 90K. This sample has the maximum critical current
density (Jc=1.52x104A/cm2). The critical current density Jc and I-V
characteristics for the present Y358/Ni-Zn nanoferrite composie materials can
be explained according to Bean,s critical state model and charge-vortex duality
in Y358 high-Tc mixed-state type-II superconductor.