Structural characterization and superconducting properties of MgB2 prepared by SHS-method

Abstract

Self-propagating high-temperature synthesis (SHS) of bulk MgB2 superconductor from Mg-2B powder blend is reported. This reaction proceeds violently at 100 A under a protective atmosphere. Since the heat of reaction of Mg and B was not enough for chain reaction, then (Ti + C) mixed powders were used as the ignition agent to assist the reaction (Mg + 2B). In this case, the combustion front moved without any difficulty. The diffraction lines of the product can be indexed to a hexagonal MgB2 phase, with lattice constants a = 3.0845 A, and c = 3.5259 A. For comparison, the direct synthesis of (Mg + 2B) mixture was carried out at (800°C–1000°C). It can be found, that high-temperature sintering (1000°C) will induce the formation of impurities. The MgB2 grains are fine, well compacted and more homogenous. The structure of materials was studied using XRD, FESEM and EDX. M-H curvatures were measured under the magnetic fields between −80 kOe and 80 kOe. J c was calculated from width of magnetization hysteresis loops based on the extended Bean Model.