Papers by Author: I. Kirschner

Abstract: Effects of high-energy, heavy ion irradiation on the properties of Y-Ba-Cu-O high-Tc superconductors are examined. The irradiating medium consists of accelerated Bi-ions, having atomic weight of 114.82. The detected hysteresis loops have very different forms and sizes in unirradiated and in irradiated states, referring to the strong effect of the irradiation. Striking variations of critical current- and magnetic parameters up to the extent of 30-40% in this series of specimens were detected. Their direct reason can be looked for in the change of the atomicmolecular microstructure of the specimens, as an effect due to the irradiation. This is decided by both of the energy and density of the ions arriving onto the surface of the samples [1,2]. It means that the effect produced by the irradiating individual ions depends also on the exact local place of the specimens, on nanometer scale, determined by their given molecular structure, bonding relationships and microstructural stability. In this way, the irradiation experiments can provide some new information on the atomic-molecular properties of the specimens in question. As a genuine smart material, the Y1Ba2Cu3O7-d high-Tc superconductor is able to reply to any external influence, changing its own qualities according to that effect.

Abstract: Different high-Tc superconducting Y-Ba-Cu-O samples of slabs and rings have been investigated. Using differently prepared Y1Ba2Cu3O7-d materials, significant deviations between irradiated and unirradiated specimens have been detected in their properties. These investigations demonstrate that unlikely prepared superconductors are differently sensitive to the external irradiation, although they have the same composition. The irradiation applied during these experiments consisted of high-energy Bi-ions with the flux of 5x1010 ions/cm2 and with the energy of 720 MeV. As is experienced, a considerable variation of the magnetic moment in the extent of 19-44% and a significant increase of the critical current density up to 41% can be detected. These originate from the change of the properties of materials due to the irradiation. For the evaluation of the experiments a new fitting method is elaborated for the temperature dependence of the critical current density, providing fully correct results for the whole temperature interval. The A.C. magnetic measurements show, that the irradiation causes to reach the state of the perfect diamagnetism at higher temperatures, than in the case of unirradiated samples. Similarly, the irradiated specimens have much lower losses, than the unirradiated ones and even these smaller values disappear at low temperatures.