The superconductivity and lattice properties (figure 15) of sintered material were investigated under pressures of up to 10GPa. The transition temperature was found to decrease linearly with increasing hydrostatic pressure, at a rate of 1.03K/GPa. This could be explained by the classical Bardeen–Cooper–Shrieffer theory, based upon an electron–phonon coupling mechanism. The crystal lattice exhibited an anisotropic compressibility, characterized by a larger compressibility along the c-direction than the a/b-directions. The anisotropy was attributed to a weaker inter-plane bonding along the c-axis in comparison with a stronger intra-plane bonding perpendicular to the c-axis. The bulk modulus of the measured material was deduced to be 172GPa.

Structural and Electronic Properties of Superconductor MgB2 under High Pressure. J.Tang, L.C.Qin, H.W.Gu, A.Matsushita, Y.Takano, K.Togano, H.Kito, H.Ihara: Journal of Physics - Condensed Matter, 2002, 14, 10623-6

Figure 15

Lattice Parameters as a Function of Pressure

(Normalized with respect to ambient pressure)