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Beirut, Lebanon

Abdeen W.,Alexandria University | Abdeen W.,University of Umm Al - Qura | El-Tahan A.,Tanta University | Roumie M.,Accelerator Laboratory | And 4 more authors.
Journal of Magnetism and Magnetic Materials | Year: 2016

Superconducting samples of SmBa2Cu3O7−δ (Sm-123) added with various amounts of nanosized MnFe2O4 addition (0.0−0.20 wt%) were investigated. The investigated samples prepared by the solid-state reaction method. The phase formation and microstructure of these samples were examined using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), proton induced X-ray emission (PIXE) and Rutherford backscattering spectrometry (RBS). XRD data indicate that the volume fraction of Sm-123 increases as nanosized MnFe2O4 increases up to 0.02 wt%. The elemental distribution and oxygen content were deduced from PIXE and RBS. The oxygen content slightly decreases as MnFe2O4 wt% increases. The superconducting transition temperature (Tc) and critical current density (Jc) of the prepared samples were estimated from electrical resistivity and transport critical current density measurements. It was found that Tc decreases as nanosized MnFe2O4 addition increases, while Jc enhances up to 0.02 wt%. Moreover, the temperature dependence of normal state electrical resistivity was studied in view of the pseudogap opening in order to determine the pseudogap temperature T* as a function of nanosized MnFe2O4 addition. T* increases as nanosized MnFe2O4 increased, indicating the enhancement of the pseudogap formation in HTSCs by adding magnetic impurities. The crossover to fluctuation conductivity near the Tc is discussed. © 2016 Elsevier B.V. Source


Mawassi R.,Beirut Arab University | Awad R.,Alexandria University | Roumie M.,Accelerator Laboratory | Kork M.,Beirut Arab University | Hassan I.,Alexandria University
Advanced Materials Research | Year: 2011

The major limitation of Bi-system superconductor applications is the intergrain weak links and weak flux pinning capability producing low critical current density of the Bi-based phases. In order to enhance these characteristics and other superconducting properties, effective flux pinning centers are introduced into high temperature superconductors. In this work, different weight percentages of ZnO nano oxide were introduced at the final stage of the Bi1.8Pb0.4Sr2Ca2Cu 3O10-y superconductor preparation process. Phase characterization was completed by X-ray diffraction (XRD). Exact constitution of the samples was determined using particle induced X-ray emission (PIXE). Granular and microstructure were investigated using scanning electron microscopy (SEM). Electrical resistivity as function of the temperature was carried to evaluate the relative performance of samples, and finally, E-J characteristic curves were obtained at 77K. Using 0.4 ZnO weight percentage, the electrical and granular properties were greatly enhanced, indicating more efficient pinning mechanisms. A critical current density of 949 A/cm2 was obtained which represents more than twice the value obtained for the pure sample (Jc= 445 A/cm2). © (2011) Trans Tech Publications, Switzerland. Source


Mawassi R.,Beirut Arab University | Marhaba S.,Beirut Arab University | Roumie M.,Accelerator Laboratory | Awad R.,Beirut Arab University | And 3 more authors.
Journal of Superconductivity and Novel Magnetism | Year: 2014

Bi1.8Pb0.4Sr2Ca2Cu 3O10+δ superconductor samples were synthesized by the conventional solid-state reaction technique. Nano-Ag was introduced by small weight percentages (0.2, 0.4, 0.6, 1, and 1.5 weight %) in the final step of the synthesis process. Phase formation and microstructure were investigated using x-ray powder diffraction, differential scanning calorimetry, and scanning electron microscopy. The real elemental-content and oxygen-content were examined using particle induced X-ray emission (PIXE) and Rutherford backscattering (RBS) techniques, respectively. Electrical resistivity as function of the temperature was carried to evaluate the relative performance of samples. Moreover, Electric field-Current density (E-J) characteristic curves were measured at 77 K. The electrical and granular properties were greatly enhanced, indicating more efficient pinning mechanisms. An improvement of the critical current density of 229 % was obtained with x=0.6 wt.%, while the superconducting transition temperature is improved by 2.5 %. © 2013 Springer Science+Business Media New York. Source


Roumie M.,Accelerator Laboratory | Abdeen W.,Alexandria University | Awad R.,Beirut Arab University | Awad R.,Alexandria University | And 3 more authors.
Journal of Low Temperature Physics | Year: 2014

Superconductor samples of type Bi1.8Pb0.4Sr 2Ca2Cu3O10+δ added with nano ZnO and Fe2O3 were synthesized by the conventional solid-state reaction technique. The samples were characterized using X-ray powder diffraction (XRD), scanning electron microscope (SEM), differential scanning calorimetry (DSC) and electrical resistivity measurements. Excess conductivity analysis of the investigated samples was carried out as a function of temperature using Aslamazov and Larkin (AL) model. The analysis showed four different fluctuation regions namely critical (cr), three-dimensional (3D), two-dimensional (2D) and short-wave (sw). The zero temperature coherence length along c-axis, effective layer thickness of the two-dimensional system and inter-layer coupling strength were estimated as a function of nano-oxides concentration. In addition, the thermodynamics, lower and upper critical magnetic fields as well as critical current density were calculated from the Ginzburg number NG . It was found that the low concentration of nano-ZnO addition up to x=0.2 wt.% improved the physical properties of (Bi,Pb)-2223 phase. In contrary, these properties were deteriorated for x>0.2. These results indicated that the addition of a low amount of nano-ZnO during the final processing of (Bi,Pb)-2223 samples can be effectively improved the flux pinning ability, while the addition of a high amount of nano-ZnO decreased the volume fraction and increased the resistance of grain boundaries. Moreover, the addition of nano-Fe2O3 had a negative effect on the superconducting parameters of the (Bi,Pb)-2223 phase. This behavior was attributed to the decrease in the volume fraction of (Bi,Pb)-2223 phase with the increasing of nano-Fe2O3. © 2013 Springer Science+Business Media New York. Source


Awad R.,Alexandria University | Al-Zein A.,Ecole Centrale Paris | Al-Zein A.,Beirut Arab University | Roumie M.,Accelerator Laboratory | And 2 more authors.
Journal of Materials Science and Technology | Year: 2013

X-ray powder diffraction, scanning electron microscopy (SEM), energy dispersive X-ray, electrical resistivity and AC-magnetic susceptibility measurements have been performed for polycrystalline superconducting samples of type TlBa2Ca2-xScxCu3O9-δ (0.0≤x≤0.6). The powder X-ray diffractograms indicate that the tetragonal structure of Tl-1223 is not affected by Sc-substitution whereas the lattice parameters are changed. The X-ray analysis indicates that the low-contents of scandium (x) enhance the formation of Tl-1223 and reduce the secondary phases. The grain-size determined by SEM decreases as x increases. The electrical resistivity measurements show suppression in the superconducting transition temperature, Tc, and an increase in both the residual resistivity and the superconducting transition width as x increases. The suppression in Tc is attributed to the hole-filling mechanism. © 2013. Source

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