MgB₂ Wires and Bulks With High Superconducting Performance

Abstract

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 MgB₁.₈₋₂.₄ O₀.₀₄₋₀.₇₁ C₀.₁₂₋₀.₁₆) demonstrated J c (20 K, 2 T) = 10⁵ A/cm² , J c (4.2 K, 15 T) = 2 × 10³ A/cm² 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 × 10³ A/cm² and J c (20 K, 6 T) = 4 × 10³ A/cm².