Property studies of MgB2 superconductor directly synthesized using high pressure

Polycrystalline MgB2 with a sharp superconducting transition at 39 K was directly synthesized from the elements using high pressure. The sample showed high critical current densities. The electron energy-loss spectrum of B shows the peaks of σ and antibonding bonds, in good agreement with the hole-doping theoretical calculations. The pressure dependences of the sound velocities were measured up to 0.5 GPa, and subsequently elastic moduli, the Debye temperature and the specific heat were calculated. The isothermal Murnaghan equation of state of MgB2 is established. Also, the pressure coefficient of the phonon frequency and the volume dependence of the electron-phonon coupling constant are calculated