Microstructure of MgB_2 superconducting wire prepared by internal magnesium diffusion process

摘要

We have analyzed the microstructure of dense pore-free undoped MgB_2 single filament wire made by internal magnesium diffusion process (IMD). The superconducting layer consists of nearly pure MgB_2 matrix with small volume fraction of nano-sized Mg and MgO precipitates and some of amorphous or nanocrystalline B-rich grains. Content of oxygen in IMD wire was significantly suppressed in comparison to PIT technology. Thin Mg layers were observed on plate-shaped MgB_2 grain boundaries. Electrical measurements have shown high critical current densities in MgB_2 layer, which are promising for further improvements and also for possible applications.