Correlation Between Structural Modifications and Levitation Performance in PAni-addition MgB2 Bulk Superconductors

Bayazıt T.

Gümüşhane Üniversitesi Fen Bilimleri Dergisi, cilt.15, sa.4, ss.1209-1221, 2025 (Scopus, TRDizin)

Özet

In this study, bulk MgB2 superconductors with varying polyaniline (PAni) contents (0–6 wt%) were synthesized via a closed-tube method and heat-treated at 850 °C under Ar atmosphere. Structural characterization by X-ray diffraction revealed that increasing PAni content led to systematic decreases in lattice parameters (a, c), interplanar spacing d (101), and unit cell volume, attributed to partial carbon substitution from PAni decomposition. This substitution, due to the smaller atomic radius of carbon compared to boron, modifies the crystal lattice and influences electronic structure. Crystallite size, dislocation density, and lattice strain calculations indicated that low-to-moderate PAni additions increase defect density and microstrain, potentially enhancing flux pinning. SEM analysis showed notable microstructural changes, including reduced porosity and improved homogeneity at lower adding, while higher contents promoted grain growth. Magnetic levitation force measurements under field-cooled (FC) and zero-field-cooled (ZFC) conditions showed that optimal PAni additions (4.5–6 wt%) improved the maximum levitation force in FC mode, while higher adding levels caused a decline in the initial force in ZFC mode, as observed at both 20 K and 25 K. The results establish a direct link between lattice parameter modification and levitation performance, offering insights for tailoring MgB2-based superconductors for magnetic levitation applications.