Hussein Baqiah

Role of Nd2O3 nanoparticles addition on microstructural and superconducting properties of YBa2Cu3O7-δ ceramics

Abstract The effects of Nd2O3 nanoparticles addition on microstructure, transport and AC susceptibility properties of YBa2Cu3O7-δ (Y123) superconductors were systematically investigated using X-ray diffraction (XRD), scanning electron micrograph (SEM), four point probe measurement and AC spectrometer. It was found that the added samples were predominant by Y-123 phase beside small amount of Y-211 and unreacted Nd2O3 secondary phases. All added samples preserved the orthorhombic structure similar to the pure sample and no orthorhombic-to-tetragonal transition occurred. The samples became more porous and their grain size significantly decreased with addition of Nd2O3. The addition of nano-Nd2O3 disturbed the grain growth of Y123, thus resulting in the degradation of superconducting properties of the samples. The superconducting transition temperature (Tc onset) of samples decreased from 92 K for x=0.0 to 78 K for x=1.0 wt.%, which could be attributable to oxygen vacancy disorder. From AC susceptibility result, the inter- and intra-granular loss peaks became wider and broader with increase of Nd2O3 addition due to the weakening of grains coupling. On the other hand, the inter-granular critical current density, Jcm, was found to increase with Nd2O3 addition and had the highest value at x=0.6, confirming that Nd2O3 nanoparticles acted as pinning centers in Y123 matrix.

High magnetic saturation of undoped and cobalt-doped tin oxide prepared by sol–gel method annealed in air and nitrogen gas

High transparent Sn1−xCoxO2 (x = 0.00, 0.02, 0.04, 0.06, 0.10, 0.20) nanocrystalline thin films were prepared by a simple sol–gel method followed by a spin-coating technique then annealed in air and nitrogen gas. The effect of Co concentration and nitrogen gas on the structural, electrical, optical and magnetic properties of Sn1−xCoxO2 was investigated using X-ray diffractometer, ultraviolet–visible spectroscopy, Hall Effect measurement system and vibrating sample magnetometer. The X-ray diffractometer patterns show that all of the films have good crystallization except some samples that annealed in nitrogen gas have extra peak corresponding to Sn7O(OH)2Cl2. The resistivity of samples annealed in nitrogen gas increased as Co concentration increases; however, the samples annealed in air showed higher resistivity that was impossible to measure. The optical transmittance of films annealed in nitrogen gas increased from 90 to 98%. The band gap obtained was 3.84 and 3.98 eV for pure sample annealed in air and nitrogen gas, respectively and increased as Co concentration increases. Ferromagnetic behavior was obtained from all samples while 10% Co-doped SnO2 annealed in nitrogen had highest saturation magnetization. This study revealed that annealing samples in nitrogen gas improved the physical property of samples.Graphical Abstract

Effects of Calcination Temperature on Microstructure and Superconducting Properties of Y123 Ceramic Prepared Using Thermal Treatment Method

Thermal treatment method was employed to produce YBa2Cu3Ox superconductor ceramic. The effects of calcination temperature at 850 °C, set A, and 910 °C, set B, for 24 h followed by sintering at 930, 950 and 980 °C, were investigate using X-ray diffraction (XRD), scanning electron microscope (SEM) and four point probe measurement. The orthorhombic structure appears after calcination at 850 and 910 °C beside small amount of impurity phase such as Y2BaCuO5 (Y211). The samples exhibited metallic behaviour and the critical temperature, TC(R=0), increases with increasing sintering temperature. The TC(R=0) of samples calcined at 910 °C is higher than that of sample calcined at 850 °C. The highest TC(R=0), 87 K, was found for sample sintered at 980 °C of set B. An increase in grain size and homogeneity was observed as the sintering temperature increases. The set B sample sintered at 980 °C showed compact grains, which could result in the highest Tc (R=0).