Polycrystalline samples were prepared by a solid-state reaction using Mg and B powders. The resistance measurements showed that the onset transition temperature and zero resistance transition temperature were 43.8K and 37K, respectively. The latter strongly depended upon the measuring current. A diamagnetic transition temperature of ~38K was found using alternating-current susceptibility measurements. The X-ray powder diffraction spectra could be indexed using an hexagonal structure with space-group, P6/mmm and lattice parameters a = 0.30864 and c = 0.35212nm. A second phase, probably MgO, was also found.

Preparation and Characterization of the New Superconductor MgB2. Y.Sun, W.H.Song, J.M.Dai, X.C.Wu, K.Y.Wang, B.Zhao, H.Xiao, J.J.Du, H.H.Wen, Z.X.Zhao: Chinese Physics Letters, 2001, 18, 587-8