Comparison of SiC and/or toluene additives to the critical current density of internal Mg diffusion-processed MgB2 wires

The internal Mg diffusion (IMD) process produces a MgB2 layer with higher density than that achieved with the traditional Powder-in-tube (PIT) method; this makes the IMD process an attractive one for the fabrication of superconducting MgB2 wires with higher critical current densities (Jc). We have recently shown that co-addition of SiC and some liquid aromatic hydrocarbons (toluene and dimethylbenzene) can enhance the Jc of IMD-processed mono-core MgB2 wires. In the present contribution, we discuss the Jc of the IMD-processed mono-core MgB2 wires fabricated under different conditions, viz. with pure B powder, B powder with additive-like SiC or toluene, and B powder with SiC + toluene co-addition. The results from these samples indicated that the SiC + toluene co-addition gave the best Jc value, as in the previous results. The composition and microstructure suggested that carbon substitution for boron and reductions of grain size by SiC and/or toluene additives are responsible for the Jc enhancements of IMD-processed MgB2 wires.

► SiC and/or toluene additives can enhance Jc of IMD processed MgB2 wire. ► SiC + toluene co-added MgB2 wire showed a Jc value of 50 kA/cm2 at 10 T and 4.2 K. ► The amount of C substitution for B increased by the additives. ► Toluene addition reduces the grain size of IMD processed MgB2. ► C substitution for B and reduction of grain size are responsible for Jc enhancement.