Vol.30 No.1(4) [2008]

Transmission Electron Microscopy Observation of MgB2 Superconducting Materials with Inhomogeneous Microstructure: Influences of Specimen Preparation Methods

Satoshi HATA, Harini SOSIATI, Takeshi YOSHIDOME, Noriyuki KUWANO, Akiyoshi MATSUMOTO, Hitoshi KITAGUCHI and Hiroaki KUMAKURA


Transmission electron microscopy (TEM) observation of microstructure in MgB2 superconducting materials was carried out using different TEM specimen preparation methods. When a focused ion beam microsampling (FIB-MS) technique was applied to prepare thin foil specimens, TEM observation revealed inhomogeneous microstructure in MgB2 tapes fabricated by an in situ powder-in-tube (PIT) process: the microstructure composed of a densely crystallized MgB2 area, a partially crystallized area containing amorphous phases, micro-meter sized holes, etc. It was also revealed that doping with SiC in the PIT process makes distribution of the crystallized and partially crystallized areas uniform. On the other hand, when a conventional TEM specimen preparation, pulverizing the specimen into powders and thinning the powders with an Ar ion mill was performed, the microstructural characters of the MgB2 tapes described above were hardly recognized.