Formation of magnesium diboride-based materials with high critical currents and mechanical characteristics by high-pressure synthesis
The developed method of high-pressure synthesis (HPS) allows producing nanostructural highly dense material based on MGB2, which possesses the highest superconducting and mechanical characteristics among the known world analogues, in the form of blocks that are suitable for application in SC electromotors and pumps. Additions of Zr can increase critical current density (jc) of synthesized at 2 GPa and 750-800 °C MGB2 in the same manner as additions of Ta or Ti, i.e. due to the absorption of impurity hydrogen forming the ZrH2. The formation of ZrB2 phase at higher synthesis temperatures (about 950 °C) in HPS MGB2 does not result in the jc increase. Some increase in jc of HPS MGB2 at 10 K in the fields higher than 8 T was observed when nano-SiC was added. The additions of Zr, Ta or Ti can prevent the harmful MgH2 impurity phase from appearing and hydrogen from being introduced into the material structure. Besides, the presence of additions in HPS MGB2 promotes the formation of a larger amount of Mg-B (most likely MGB2) inclusions in the Mg-B-O material ''matrix'' that in turn leads to the increase of jc of the material in magnetic fields.
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