Papers by Keyword: Bulk Superconductor

Abstract: This paper describes the details on synthesizing nanocrystalline Gd2BaCuO5 (Gd211) using low-temperature combustion synthesis(LCS). The morphology and structure of the powders are characterized by field emission scanning electron microscopy (FESEM) and XRD. The size of obtained powders by this method calcined at 800
C is about 100nm, which is much smaller than the powders synthesizing by conventional solid state route. Besides, the Gd211 powders synthesizing by LCS have a low calcination temperature with a high-purity. The microstructure of melt-textured samples is also observed by FESEM, the result shows that the size of Gd211 particles trapped in GdBa2Cu3O7 (Gd123) matrix could be refined by using ultrafine Gd211 powder as a precursor. The refined Gd211 particles with a good distribution resulted in the improvement of Jc values in this system.

Abstract: The issues in the conventional sintering of the MgB2 superconductors have conducted to the discovery of a new way to densify this material. The new process is an “in situ” method that relies on the reactive liquid infiltration (RLI) of liquid Magnesium into Boron powders packed preform. The RLI process allows to obtain highly dense manufacts without the use of hot pressing apparatus and can be applied to the manufacture of large superconducting pieces. One of the peculiarities of the MgB2 superconductivity, that withstand up to 39 K, is represented by the relative insensitiveness of the supercurrent percolation to the orientation of the grain boundaries. This property allows to use polycrystalline material without loosing superconducting performance, granted that a good connectivity between the crystalline grains must be realized, as the RLI process allows to do. The microstructure of the bulk material obtained by RLI shows a variety of morphologies, according to the kind of the used Boron powders and to the process variables. A detailed analysis of the microstructure of the MgB2 obtained by RLI will be presented, as well as its analytical description and the correlation with the superconducting characteristics.