The microstructures of samples sintered at high temperatures under a pressure of ~3GPa were investigated by using high-resolution transmission electron microscopy. The transmission electron micrographs did not exhibit any pores in the specimen. All of the grains were compactly connected, and no discernible empty spaces or impurities at the boundaries existed over the regions investigated. The transmission electron microscopic images clearly showed each constituent atom that formed the basal hexagonal plane. The density (Archimedes method) corresponded almost to the theoretical value of the bulk sample. The transmission electron micrographs support the view that MgB2 powder could be sintered, under high temperatures and pressures, to its theoretical density without producing any porosity or grain growth.

High-Resolution Transmission Electron Microscopic Observation of Highly Dense MgB2 Superconductors. G.Y.Sung, S.H.Kim, J.Kim, D.C.Yoo, J.W.Lee, J.Y.Lee, C.U.Jung, M.S.Park, W.N.Kang, Z.Du, S.I.Lee: Superconductor Science and Technology, 2001, 14, 880-3