Effects of high pressure on the physical properties of MgB ²

The synthesis of MgB ₂-based materials under high pressure gave the possibility to suppress the evaporation of magnesium and to obtain near theoretically dense nanograined structures with high superconducting, thermal conducting, and mechanical characteristics: critical current densities of 1.8-1.0 × 10 ⁶ A/cm ² in the selffield and 10 ³ A/cm ² in a magnetic field of 8 T at 20 K, 5-3 × 10 ⁵ A/cm ² in self-field at 30 K, the corresponding critical fields being H _c2 = 15 T at 22 K and irreversible fields H _irr = 13 T at 20 K, and H _irr = 3.5 T at 30 K, thermal conduction of 53 ± 2 W/(m·K), the Vickers hardness H _V = 10.12 ± 0.2 GPa under a load of 148.8 N and the fracture toughness K _1C = 7.6 ± 2.0 MPa·m ^0.5 under the same load, the Young modulus E = 213 GPa. Estimation of quenching current and AC losses allowed the conclusion that high-pressure-prepared materials are promising for application in transformer-type fault current limiters working at 20-30 K.