Fine structure of a bulk MgB2 superconductor after deformation and heat treatment
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The structure of the MgB2 superconductor subjected to high-temperature restoration annealing after cold deformation under high pressure in a Toroid chamber or Bridgman anvils has been investigated by transmission electron microscopy. It has been shown that after postdeformation annealing at 950°C the average size of crystallites in the matrix phase increases 5–10 times compared to the deformed state, reaching ~50–150 nm, as well as the critical current density increases by a factor of three (up to 6.7 × 104 A/cm2, 30 K) compared to the initial state. It has been found that the MgO phase and the higher magnesium borides are present in the form of dispersed precipitates 10–70 nm in size.
Keywordsmagnesium diboride deformation annealing
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