A. Hassen

Influence of Cr2O3 nanoparticles on the physical properties of polyvinyl alcohol

Nano-sized chromium oxide (Cr2O3) was synthesized by sol-gel method and mixed with polyvinyl alcohol (PVA) to produce nanocomposite films. Scanning electron microscopy (SEM) was used to observe the morphology and dispersion of Cr2O3 on the surface of the PVA films. X-ray diffraction (XRD) was performed on nano-sized Cr2O3, pure PVA, and Cr2O3/PVA composites. Based on the results of both XRD and high-resolution transmission electron microscopy (HR-TEM), the average particle size of the Cr2O3 was ≈ 46 nm. Differential scanning calorimetry (DSC) showed that the thermal stability and degree of crystallinity of the PVA were reinforced by the addition of Cr2O3 nanoparticles. The absorbance and extinction coefficients of the composites were studied in the UV-vis range and compared with those of pure PVA. The optical energy band gap, Eg, was calculated. Dielectric constant, e′, dielectric loss modulus, M″, and ac conductivity, σac, of all samples were measured within temperature and frequency ranges of 300–468 K ...

Structural, transport and magnetic properties of Ru1-xMxSr2GdCu2O8 (M = Ti and Rh for 0 ≤ x ≤ 0.2)

Abstract We report on structural, electrical and magnetic properties of Ru 1− x M x Sr 2 GdCu 2 O 8 , with M=Ti and Rh for 0⩽ x ⩽0.2. The polycrystalline samples were synthesized by conventional solid-state reaction. There are no significant structural changes on partially substituting Ru by Ti or Rh within the studied level of doping. Both ferromagnetic (FM) and superconducting (SC) transition temperatures are reduced upon increasing doping concentration. In the Ti-doped compounds, the corresponding SC and FM transition temperatures decrease significantly faster than in Rh-doped samples. The superconductivity becomes fully suppressed at x =0.1 for Ti and x =0.2 for Rh, respectively. The presented results are compared with published work on different substitutional defects and a generalized phase diagram is established.

Transport and magnetic properties of Ru(Sr1−xLax)2RCu2O8 (R=Gd, Eu) superconductor

Abstract The resistivity, thermopower and magnetic properties have been investigated systematically in the ferromagnetic superconductors Ru(Sr 1− x La x ) 2 RCu 2 O 8 (R=Gd and Eu), in which carrier density has been reduced by partial replacement of Sr by La ions. With increasing x both the resistivity and thermopower are found to increase whereas superconducting transition temperature T c shows a considerable decrease and the system becomes more and more underdoped. Based on our results, we conclude that similar to other high- T c materials, superconductivity appears in the vicinity of insulator to metal transition point at around 0.04 holes/Cu.

Structural, Transport and Magnetic Properties of the Doped Magnetic Superconductor Ru‐1212

Single phase materials of RuSr2Gd0.5Eu0.5Cu2O8 (Ru‐1212Gd0.5Eu0.5) and Ru(Sr1−xNax)2GdCu2O8 (0 ⩽ x ⩽ 0.10) have been successfully synthesized in oxygen at 1065 °C. DC‐resistivity and magnetic susceptibility measurements show a decreases of the superconducting transition temperature Tc from 46 K in the pure Gd compound to 41 K in Ru‐1212Gd0.5Eu0.5, whereas the magnetic ordering temperature TM does not change. The influence of the monovalent substitution Na+ for Sr2+ on the properties of Ru‐1212Gd is investigated and compared with previous work. Finally, the effects of Cu substituted RuSr2Gd(Cu1−xMx)2O8 compounds, where M is Co, Ni and Ga for 0 ⩽ x ⩽ 0.03 are reported and compared with similar doping experiments in other high‐Tc superconductors.