MgB2 Wires and Bulks With High Superconducting Performance

The critical current density at 4.2 and 20 K up to 15 T and the temperature dependence of the irreversible field have been studied in magnesium diboride wires and bulks prepared from boron without and with carbon addition. Structural investigations using X-ray microprobe analysis have been performed. A monofilamentary wire with a round-shaped core manufactured from boron containing 2 mol.% carbon (approximate composition of its matrix MgB
_1.8-2.4
O
_0.04-0.71
C
_0.12-0.16
) demonstrated J
_c
(20 K, 2 T) = 10
⁵
A/cm
²
, J
_c
(4.2 K, 15 T) = 2 × 10
³
A/cm
²
and B
_irr
(20 K) = 8 T, B
_irr
(12.5 K) = 15 T. Bulk material synthesized at 2 GPa, 600 °C, 1 h from carbon doped boron demonstrated J
_c
(10 K, 10 T) = 4 × 10
³
A/cm
²
and J
_c
(20 K, 6 T) = 4 × 10
³
A/cm
²
.