Microstructure and J/sub c/-B performance of powder-in-tube MgB/sub 2/ wire made by using Mg/sub 2/Cu powders with low melting point

MgB/sub 2/ superconducting wires can be synthesized through a new route by using Mg/sub 2/Cu instead of pure Mg. The brittle Mg/sub 2/Cu compound can be easily broken into the fine powders by a mechanical grinding. In addition, its melting point are lower than that of pure Mg, thus the diffusion reaction for synthesizing MgB/sub 2/ may be promoted through their liquid states. Both of J/sub c/ and B/sub irr/ at 4.2 K improved apparently with decreasing the size of Mg/sub 2/Cu powders as a starting material. 100 A/mm/sup 2/ was obtained at 4.2 K and 4 T on the Fe-sheathed MgB/sub 2/ wire made by using Mg/sub 2/Cu powder with a diameter of a few microns. These improvements may be due to the enhancement of homogeneity of the powder mixture. According to the STEM observation, a lot of small MgCu/sub 2/ particles with a size of about 10 nm were dispersed in the MgB/sub 2/ matrix synthesized through a fine Mg/sub 2/Cu powders. They may act as the pinning centers in the present MgB/sub 2/ wires.