HIGH-PRESSURE SYNTHESIS OF MgB₂ SUPER-CONDUCTOR WITH T_c ABOVE 39 K

We report on the high-pressure synthesis and superconductivity of MgB₂ intermetallic compounds. The compounds have been obtained through high-pressure sintering of the mixtures of magnesium and boron fine powders under 5.0 GPa and at ～1000℃ for 30 min. Magnetic measurements using a SQUID magnetometer show the sharp bulk superconducting transition above 39 K; the four-probe dc resistivity measurements indicate the highly-conductive normal state and sharp superconducting transition. The results highlight that high-pressure synthesis would be a promising way to promote the studies of this new kind of intermetallic superconductors.