Microstructure and pinning in high- and large- (Nd, Eu, Gd)-123 superconductors prepared by OCMG process

Abstract

The effects of (NEG-211), Pt and additions on OCMG-processed (`NEG') composites have been investigated in detail using a combination of scanning electron microscopy and measurements of critical current densities, . Microstructural observations clearly indicated that the platinum addition was effective in refining the NEG-211 secondary-phase particles, which led to a dramatic increase in in the low-field as well as in the high-field region. TEM-EDX analyses revealed that the small secondary-phase particles (diameter ) consist mainly of Gd in the rare earth site, while the large particles contain Nd, Eu and Gd in the rare earth site with an even ratio, which is identical to the nominal composition of the precursor powder. For an NEG sample with 40 mol% NEG-211 additions, a large critical current density of 60 000 A at 77 K was observed in a magnetic field of 3 T applied parallel to the c-axis of the sample. The critical current density measurements showed that the zero field and peak values are similar in samples with 30 and 40 mol% of NEG-211 added. In contrast to this, the combination of and Pt addition was not as effective in refining the NEG-211 particles, and also the values were found to decrease in the entire field region.

Synthesis and superconducting properties of Nd0.33Eu0.08Gd0.58Ba2Cu3Oz materials

“…The electromagnetic performance of LRE-Ba 2 Cu 3 O (light rare earth, LRE = Nd, Sm, Eu, Gd; LRE123) materials is much better than that of Y-123. As already shown in several reports [1][2][3] NEG-123 (NEG = Nd 1− − Eu Gd ) bulk superconductors exhibit superior pinning characteristics, uniform microstructure and good reproducibility. However, for applications above 77 K, a further pinning enhancement, especially in high magnetic fields, is needed.…”

“…The length of the c-axis observed in our samples is higher than the values observed in corresponding YBCO single-crystal sample. Rietveld refinements of crystal structure performed using X'Pert High- 1 Score Plus 2 showed that Gd, Nd and Eu atoms take as expected the Y (0.5; 0.5; 0.5) position in the crystal cell. In addition, Nd is also present in the Ba (0.5 0.5 0.18) position.…”

New Type of Vortex Pinning Structure Effective at Very High Magnetic Fields

“…In ternary compounds, combination of different light rare-earth elements on the rare-earth site enables variation of the Nd:Eu:Gd chemical ratio [8,9]. Surprisingly strong pinning at high fields was observed for a narrow range of chemical ratio around Nd:Eu:Gd 33:28:38 [10].…”

“…0.5 mol % of Pt was added to refine the secondary phase particles and 10 wt % of Ag 2 O to improve mechanical properties. All samples were fabricated by the oxygen-controlled-meltgrowth process under oxygen partial pressure of 0.1% O 2 and gas flow rate of 300 ml=min [8]. For magnetic measurements, small specimens with dimensions of about a b c 2 2 0:5 mm 3 were cut from the asgrown pellets and annealed in flowing oxygen in the temperature range (300 -600) C [8].…”

Improvement of Critical Current Densities in Bulk Superconductors of the 123-Type

“…Finally, the samples were subjected to the melt-growth process in 0.1% partial pressure of O 2 . Details of the heat treatment schedules can be found elsewhere [6].Microstructural features of the samples were observed using a H9000UHR transmission electron microscope (TEM) operating at 300 kV in conjunction with energy dispersive X-ray (EDX) analyses. Two different kinds of 211 particles are found (Fig.…”