Single-grain growth, microstructure and superconducting properties of (Sm, Eu)123 superconductors with BaCuO_2 xaddition

Abstract

High quality (Sm 0.5 , Eu 0.5 )Ba 2 Cu 3 O 7−δ single domains were grown in air with BaCuO 2−x addition. It was found that a RE-Ba substitution (RE: Sm and Eu) could be effectively suppressed by a small addition of BaCuO 2−x . The 94 K superconductivity with sharp transition was obtained in the composition range of 0.16 ∼ 0.33 BaCuO 2−x and (Sm 0.5 , Eu 0.5 )Ba 2 Cu 3 O 7−δ in a molar ratio. At 77 K, a surface field of 0.8 T was trapped in a single-domain pellet of 3.2 cm diameter. A further addition of BaCuO 2−x deteriorated the microstructure and degraded the superconducting performance.

The influence of BaCuO2 addition in Gd–Ba–Cu–O single-grain superconductors fabricated in air

“…So the improvements of superconducting transition can be attributed to the suppression of Gd-Ba substitution by doping BaCuO 2−δ . In addition, from the results of Hu et al [12,18], an excess doping of BaCuO 2−δ with x = 0.53 also leads to a decrease of T c due to segregation of BaCuO 2−δ at grain boundaries, which deteriorates the superconducting junctions.…”

“…However, from the viewpoint of batch production with considerably low cost, it is desirable that large bulks with high performance be melt processed in air. Different methods [9][10][11][12][13], such as using Ba-rich precursors, large crystallization rate and post-annealing in Ar, have been developed to suppress the LRE/Ba substitution and hence to improve the superconducting performance of the LRE-Ba-Cu-O bulks melt processed in ambient atmosphere.…”

“…In addition, previous studies [16][17][18] revealed that J c values and field-trapping properties of the Gd-Ba-Cu-O bulks melt processed in air were improved by employing a Ba-rich precursor and fine Gd211 starting powder as well as Ag addition. According to Hu et al [12,18], employing BaCuO 2−δ in the initial composition is an alternative method to form a precursor with Ba enrichment. The aim of the present work is to fabricate single-grain Gd-Ba-Cu-O bulks with enhanced superconducting properties by the top-seeded melt-growth process under ambient atmosphere, as well as to investigate the systematical influence of BaCuO 2−δ addition on the superconducting performance.…”

Stripe and Criss-Cross Patterns in High-Tc Superconductors Revealed by Atomic Force Microscopy and Scanning Tunnelling Microscopy

“…The melt-textured high-T c superconducting samples were produced using the standard procedure. [4][5][6] Since the asgrown surfaces of the samples were usually too rough to achieve good scanning results, the samples were mechanically polished prior to scanning, either dry from 12 to 0.5 mm diamond paper or wet from 320 grain SiO paper to 4000 grain SiO paper and then from 3 mm diamond polishing solution down to 40 nm colloidal silica (Struers OP-S). 7) After that, the samples were cleaned for several minutes in acetone in an ultrasonic bath and then for several minutes in an isopropanol bath.…”

Nanoscale flux pinning sites in high‐ T c superconductors

“…STM scans were done using cut Pt/Ir-tips. The melt-textured (LRE)BCO [(LRE) = light rare earths) samples were produced using the standard procedure [8][9][10]. Since the as-grown surfaces of the samples were usually too rough to achieve good scanning results, the samples were polished prior to scanning, either dry from 12 µm to 0.5 µm diamond paper or wet from 320 grain SiO paper to 4000 grain SiO paper and then from 3 µm diamond polishing solution down to 40 nm colloidal silica (OP-S) [11].…”