MgB _2 with addition of Sb _2O _3 obtained by spark plasma sintering technique

摘要

Superconducting bulks of MgB _2 with addition of Sb _2O _3 and Sb with different stoichiometric compositions ((MgB _2) + (Sb _2O _3) _x, x = 0.0025, 0.005, 0.015, and (MgB _2) + (Sb) _y, y = 0.01) were obtained by the Spark Plasma Sintering (SPS) technique. All added samples have high density, above 95% and critical temperature, T _c, of 38.1-38.6 K. This result and XRD data suggest that Sb does not enter the lattice of MgB _2. Impurity phases are Mg _3Sb _2, MgO, and MgB _4. The optimum addition is Sb _2O _3 for x = 0.005. This sample shows the critical current density, J _c(5 K, 0 T) = 4 × 10 ~5 A/cm ~2 and J _c(5 K, 7 T) = 6 × 10 ~2 A/cm ~2, while the irreversibility field, H _(irr) (5 K, 100 A/cm ~2) = 8.23 T. Indicated values of J _c and H _(irr) are higher than for the pristine sample. The mechanism of J _c and H _(irr) increase in the Sb _2O _3 added samples is complex and composed of opposite effects most probably involving morphology elements, the presence of nano metric MgB _4 and the indirect influence of oxygen or oxygen and Sb. Crystallite size of MgB _2 is decreasing when Sb-based additions are introduced and the effect is stronger for the Sb-metal addition. The sample with Sb-metal addition does not improve J _c and H _(irr) when compared with pristine sample.