Critical Currents in High-Tc Superconductors

DyBa2Cu3O7−x (DyBCO) films with MgO buffer layers were grown on Hastelloy substrates by inclined substrate deposition (ISD). An almost linear increase of the critical current with the DyBCO film thickness was observed. A maximum critical current of 1018 A cm−1 was measured for a DyBCO film with 5.9 μm thickness, yielding a critical current density of 1.7 MA cm−2 at 77 K and self-field. Transmission electron microscopy (TEM) yielded highly biaxially textured DyBCO films at all thicknesses and, thus, no significant decrease of the critical current density occurs with the film thickness. ISD yields a non-zero component of the growth direction parallel to the DyBCO (a, b)-plane since the DyBCO grows on a faceted MgO surface and avoids a-axis growth. Therefore, the ISD technology offers a unique possibility to overcome thickness limitations in coated conductor technology.

Section: Introductionmentioning

confidence: 99%

DyBa₂Cu₃O_7−xsuperconducting coated conductors with critical currents exceeding 1000 A cm⁻¹

Dürrschnabel

Aabdin

Bauer³

et al. 2012

“…However, they are often weak links (reduced J c regions) in the superconducting current path of a ceramic sample. On the other hand, boundaries may play an important role as pinning centres [1]. One way for changing (increasing) intergrain critical current density of polycrystalline materials is doping with Ag [2,3].…”

Section: Introductionmentioning

confidence: 99%

Correlation between superconducting properties and microstructure of and ceramics fabricated by the citrate gel process

Orlova

Laval

Dubon

et al. 1998

The correlation between microstructure and superconducting properties of (deficient (D) samples) and (substituted (S) samples) fabricated by the citrate gel process has been studied. In both types of samples nonsuperconducting phases such as and CuO were observed for . EDX analysis of S samples by TEM and STEM revealed the Ag content in YBCO grains to be lower than the nominal one (x) for all x in a range . Ag segregated mainly as small precipitates in boundaries, triple junctions and grains. The dependence of the critical current density on the magnetic field B obtained showed that is controlled by weak links in both cases, D and S. The measurements of at temperatures close to indicated that the weak links have SIS character in D and SNS character in S samples. Ag doping leads to an increase in the proportion of clean boundaries in S samples compared with D samples. Specific Ag precipitations of 2-5 nm size on or near clean boundaries were found in S samples for x = 0.4. This is most likely to be the reason for the improvement of in these samples by a factor of 3. Some increase in with x in D samples was observed and was probably associated with an increase in the proportion of faceted boundaries among clean ones.

“…It is well known that the difference in superconductivity between REBCO and Y-Ba-Cu-O (YBCO) is due to the formation of RE-Ba solid solution [2]. It has been reported that the flux pinning centres accounting for J c in REBCO could originate from twins [3], point defects [4], dislocations [5] and stacking faults [6]. Also, it is known that the smaller the 211-particle size, the higher the J c (H, T ) that can be obtained [7].…”

Section: Introductionmentioning

confidence: 99%

Improvement to superconductivity using small amounts of Pd addition in Sm–Ba–Cu–O materials

Chen

2003

We have studied the superconducting properties of air-processed melt-textured grown Sm-Ba-Cu-O samples with the addition of small amounts of Pd (0-1.0 wt%). The superconducting properties are enhanced with a small amount (0.1 wt%) of Pd addition, for which T c is ∼89 K and J c at 0 T and 77 K is 10 4 A cm −2 . However, both T c and J c deteriorate as the Pd addition is further increased. In addition, J c of Pd-doped samples exhibits anisotropic J c (H, T ) behaviour. Observation of the microstructures has shown that, as the Pd addition increases, the shape of the Sm 2 BaCuO 5 particles (211-particles) tends to become rectangular, and the 211-particle size increases (larger than the control sample). We have observed changes in size and morphology of the 211-particles, dislocations and unidentified nanoscale defects in the Pd-doped samples, which imply that small amounts of Pd additions can affect the microstructure as well as altering the pinning mechanism.