It was noted that MgB2 superconductors could be synthesized by using a new route involving Mg2Cu instead of pure Mg. When the heating temperature was raised to near to the melting point (568C) of Mg2Cu, the TC of powder-in-tube processed Mg2Cu/B Fe-sheathed wires rapidly increased and reached about 37.5K. The Mg2Cu, with its low melting-point, promoted diffusion reaction to form high-TC MgB2 at low temperatures. Many second phases of large size (several tens of μm) were formed, with a small amount of MgB2 in the core of Mg2Cu/B Fe-sheathed wires. However, JC had a rather high value; above 105A/cm2 at 4.2K in ambient fields. The JC estimated from a net cross-sectional area of MgB2 was expected to be very high. A Mg2Cu/plasma-splayedB/metal-substrate layered composite was also prepared. After heat treatment (600C, 10h) in vacuum, a 50µm-thick MgB2 diffusion layer was formed, having a high-density microstructure. Here, Cu was released from Mg2Cu, and gathered on the surface of the diffusion layer. This behavior was similar to that seen in the bronze process used for Nb3Sn conductors.

The Synthesis of MgB2 Superconductor using Mg2Cu as a Starting Material. A.Kikuchi, Y.Yoshida, Y.Iijima, N.Banno, T.Takeuchi, K.Inoue: Superconductor Science and Technology, 2004, 17, 781-5