Enhancement of critical current density in fast neutron irradiated melt-textured YBa2Cu3O7-x

The discovery of high-temperature superconductors stimulated many groups of researchers to study properties of these materials. From the basic point of view the most important problem is to clarify the mechanism of high-temperature superconductivity. From the practical point of view the most challenging task is to find mechanisms of strong pinning of the vortices, and thereby to obtain materials with high critical current density. The aim of this paper is to discuss problems connected with critical current limitations and to present possibilities which offer irradiation effects with respect to critical current enhancement.PACS numbers: 74.60.Ge, 74.60.Jg, 61.80.Hg MechaniSmS of critical current limitationsIn principle, there are three mechanisms which limit the critical current density, jc , in type II superconductors: depairing, decoupling, and depinning. DepairingDepairing critical current means a value of current for which the kinetic energy of supercurrent carriers is equal to the condensation energy in the superconducting state. In other words, for this value of current the superelectrons are excited over the superconducting gap and the Cooper pairs break up. According to the BCS theory the depairing critical current is inversely proportional to the coherence length ξ. In high temperature superconductors (IITSC), due to a very small value of Ę, this current is quite large (10 9 A/cm2 at low temperatures), therefore from the practical point of view this process is not the real limitation.(139)

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“…More details concerning experiments discussed above are presented in the papers of Puźniak et al [71,72].…”

Section: Melt-textured Materialsmentioning

confidence: 99%

Critical Current Limitations and Irradiation Effects in High-Temperature

et al. 1993

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“…The influence of irradiation on the critical current density and on the pinning potential was recently studied -by mainly magnetization measurements for the cases of single-crystals [14~16] and of melt textured samples [17,18]. These results explain well the response to irradiation only for highly ordered materials (particular case).…”

Section: Introductionmentioning

confidence: 99%

Low-dose irradiation effects produced by 14 MeV neutrons in different quality Y- and Tl-based high-T c ceramics

Csikai

Kirschner

1994

Z. Physik B - Condensed Matter

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Various changes in the microwave absorption signals of irradiated samples of different quality YBa2Cu30 7 and T12CaBa2Cu2Os target materials by lowdose (1014 n/cm 2) monoenergetic neutrons have been observed and studied. The irradiation induced changes of the shape of microwave absorption lines together with transport measurements show that the low-dose irradiation in poor quality samples increases, while in good quality ones, decreases the superconducting volume fraction. Low quality (non-percolative) samples are more sensitive to irradiation than the high quality ones. These observations indicate that the consequences of irradiation are determined mainly by the preirradiation structure of the samples.

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