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 (J_c). We have recently shown that co-addition of SiC and some liquid aromatic hydrocarbons (toluene and dimethylbenzene) can enhance the J _c of IMD-processed mono-core MgB₂ wires. In the present contribution, we discuss the J_c 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 J_c 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 J_c enhancements of IMD-processed MgB₂ wires.