Addition of Sb2O5 into MgB2 Superconductor Obtained by Spark Plasma Sintering

High-density (92–98 % of the theoretical density) MgB 2 samples added with Sb 2 O 5 ((MgB 2)+ (Sb 2 O 5) x ,x= 0, 0.0025, 0.005, 0.015) were obtained by Spark Plasma Sintering. A higher amount of additive decreases density. In added samples, grains of secondary phases are located at MgB 2 grain boundaries and they are of large size. Hence, Sb 2 O 5 does not promote effective flux pinning, connectivity is lower, and this suppresses the critical current density and the irreversibility field. Pinning force-related parameters indicate that added samples are close to the point pinning region and they show a higher grain boundary pinning contribution when compared with pristine MgB 2 sample and when temperature is lower. It is speculated that for fixed processing conditions and Sb-oxide phases, a lower stability of the additive, reflected by a lower melting temperature, may promote reactive processes to start earlier leading to coarsening of the grains belonging to secondary phases.