Microstructure and Jc-B performance of powder-in-tube MgB2 wire made by using Mg2Cu powders with low melting point

MgB₂ superconducting wires can be synthesized through a new route by using Mg₂Cu instead of pure Mg. The brittle Mg₂Cu 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 MgB₂ may be promoted through their liquid states. Both of J_c and B_irr at 4.2 K improved apparently with decreasing the size of Mg₂Cu powders as a starting material. 100 A/mm² was obtained at 4.2 K and 4 T on the Fe-sheathed MgB₂ wire made by using Mg₂Cu 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 MgCu₂ particles with a size of about 10 nm were dispersed in the MgB₂ matrix synthesized through a fine Mg₂Cu powders. They may act as the pinning centers in the present MgB₂ wires.