Influence of on-off pulsed current pattern on processes during spark plasma sintering of MgB2 superconductor

Abstract

High density samples (92–94.5 %) of MgB2 were prepared by Spark Plasma Sintering (SPS). The on-off pulsed current patterns of SPS processing were 8–4, 12–2, 24–2, 99–1. Patterns with more on pulses favor formation of a higher amount of the secondary MgB4 phase through the decomposition of MgB2. They also promote enhancement of larger MgO crystallites without a strong increase in the amount of this phase. Densification rate and pressure in the SPS chamber show a similar behavior, but their amplitude varies and the temperatures defining different stages present some shifts. As-revealed differences induced by pulsed patterns impact superconducting properties in a complex manner. An attempt to assess correlations between the pattern and different superconducting parameters is presented.

Keywords

• MgB2
• Spark plasma sintering
• On-off pulse pattern
• Superconducting characteristics