Ge-Added MgB2 Superconductor Obtained by Ex Situ Spark Plasma Sintering

Abstract

Spark plasma sintering (SPS) was applied for fabrication of dense (relative density > 97 %) bulk MgB 2 samples added with Ge. Mixtures of MgB 2 and Ge powders with starting compositions (MgB 2 )Ge x , x = 0.005, 0.01, and 0.03 were used. Added samples show enhancement of the critical current density at high magnetic fields when compared to a pristine reference sample. The optimum composition is for x = 0.005 and for this sample J c (20 K) = 10 2 A/cm 2 is obtained at 5 T, while for the reference sample is obtained at 3.9 T. Ge does not substitute in the crystal lattice of MgB 2 and T c,onset or T c,midpoint from magnetization measurements scatter within 0.15 or 0.3 K, respectively.

GeO 2 -added MgB 2 superconductor obtained by Spark Plasma Sintering

“…The morphology of the Ge-containing regions has the appearance of localized grains/regions. This is different when compared with Ge-metal addition [30], where Ge shows a web-like network spread distribution although some agglomeration in the network strings was observed. The average crystallite size of MgB 2 for the samples from this work slightly decreases due to the reaction of GeO 2 with MgB 2 and following the reaction (4).…”