The superconductor was prepared in 2 ways, by high pressure and ambient pressure synthesis. The superconducting properties were measured and compared. It was found that the sample prepared by high pressure was much denser than that prepared under ambient pressure. Accordingly the high pressure sample had a very narrow transition width and a much higher bulk critical current density.

Superconducting Properties of MgB2 Prepared by High Pressure and Ambient Pressure. Z.A.Ren, G.C.Che, Z.X.Zhao, H.Chen, C.Dong, Y.M.Ni, S.L.Jia, H.H.Wen: Chinese Physics Letters, 2001, 18, 589-91