Spatial variations in superconducting and microstructural properties of bulk (Sm,Eu,Gd)Ba2Cu3O7−δ grown by top-seeded infiltration in air

The homogeneity of superconducting properties in LREBa2Cu3O7−δ bulk superconductors is crucial for their cost-effective large-scale production and practical applications across various fields. In this study, we systematically investigated the homogeneity of both the microstructural and superconducting properties of the recently developed ternary (Sm,Eu,Gd)Ba2Cu3O7−δ (SEG-123) bulk superconductors, which were fabricated in air using the top-seeded infiltration growth (TSIG) process. Samples were collected from various locations to access homogeneity across the bulk, and their microstructural and superconducting properties were analyzed using various techniques. The sample with 4 wt. % BaO2 (Ba-4) exhibited a superconducting transition temperature Tc(onset) ranging from 93.62 to 93.82 K, while the reference sample (Ba–0) showed a range of 92.61–93.51 K. Additionally, the Ba-4 sample demonstrated the sharpest superconducting transition width (ΔTc), with values ranging from 0.68 to 0.81 K, compared to the reference sample, which showed a range of 2.51–2.70 K. Microstructural analyses, including energy-dispersive x-ray spectroscopy mapping, spot analysis, and line analysis, revealed variations in the intensities of Sm, Eu, and Gd elements across the secondary (Sm,Eu,Gd)2BaCuO5 (SEG-211) phase particles and the SEG-123 matrix. These findings indicate that fabricating ternary SEG-123 bulk superconductors in air using the TSIG process can achieve homogeneous superconducting performance. Furthermore, controlling the RE/Ba and Ba/Cu ratios through BaO2 addition proves effective in enhancing the superconducting properties of air-processed SEG-123 bulk. The observed variations in element intensities within the secondary SEG-211 phase particles and the bulk matrix are of vital importance for further optimization of ternary SEG-123 bulk superconductors.