China
Africa
Explore chapters and articles related to this topic
c
Published in David A. Cardwell, David C. Larbalestier, Aleksander I. Braginski, Handbook of Superconductivity, 2023
Sergey K. Tolpygo, Thomas Schurig, Johannes Kohlmann
Superconductivity in the intermetallic compound magnesium diboride (MgB2) with a remarkably high critical temperature Tc = 40 K was discovered in 2001 (Nagamatsu et al., 2001). As a consequence of its high Tc, large coherence length, two co-existing large energy gaps (2.2 meV and 7.1 meV), high critical current densities and critical fields, it is a very promising material for superconducting electronic devices, in particular for high speed circuits (Xi, 2008). In contrast to Nb-based superconducting electronic devices, cooling of MgB2 devices to operational temperatures in the range of 20–30 K by using mechanical cryocoolers is comparatively easier. The anisotropic transport properties of the multiband superconductor MgB2 demand the availability of in-plane epitaxial thin-films for electronic device fabrication. Beside mature MgB2 thin-film deposition techniques, an elaborated multilayer thin-film technology enabling fabrication of JJs and wiring with only a minor spread in junction properties is required, e.g., of less than 2% for RSFQ circuits.
Magnesium Diboride
Published in David A. Cardwell, David C. Larbalestier, I. Braginski Aleksander, Handbook of Superconductivity, 2023
Magnesium diboride (MgB2) is a binary intermetallic compound with a simple hexagonal structure (a = 3.086 Å, c = 3.524 Å) consisting of alternating layers of boron and magnesium (Nagamatsu et al., 2001). Boron atoms form honeycomb layers stacked without displacement which generate hexagonal prisms. At their centres, large nearly spherical sites are created and occupied by magnesium atoms. As a consequence, magnesium atoms form a triangular lattice halfway between the B layers (see Figure B2.1).
Synthesis and superconducting properties of the MgB2@BaO composites
Published in Inorganic and Nano-Metal Chemistry, 2020
S. Tolendiuly, S. M. Fomenko, R. G. Abdulkarimova, A. Akishev
The positive effect of the pressure of Ar and doping with BaO during the solid-state synthesis of MgB2 powders on its critical current density Jc has been confirmed. It was found that MgB2 phase responsible for the increase of critical current. Simultaneously, an increase in the content of barium oxide in the initial mixture leads to the formation of a useful phase of BaB6, which in turn positively affects the superconducting properties of the composite based on magnesium diboride, acting as effective pinning centers. It is obviously the content of barium oxide significantly influence on the crystallite size (Table 2) in the final product of the synthesis where the grain size of all samples decreases monotonically. It is most likely, that BaB6 impurity plays a key role in enhancing of Jc parameter of MgB2 samples. Simultaneously, this question needs further investigations (as theoretical as well as empirical measurements), especially how the BaB6 phase affects the nature of grain connectivity of the sintered MgB2 sample.