Effect of irradiation by fast electrons and60Co γ-rays on superconducting and electrical properties of thallium and bismuth ceramics

Effect of magnetic field and gamma irradiation on the electrical properties and structure of the Tl-based ceramic superconductors

“…The sensitivity of the Tl-based superconductors to the low levels of γ dose may be associated with the fact that these materials are more anisotropic compared with the Bi-based superconductors. Quite a large expansion of the lattice parameters and increase in the transition temperature of the bulk and thin-film samples of the Bi-based superconductors were reported to occur with γ irradiation [10,14,16,17]. Contrary to such reports, an increase in T c or drastic change in the lattice parameters have not been observed for the γ -irradiated Tl-based ceramic superconductors studied here.…”

“…The effects of γ irradiation on the properties of the Tl-based ceramic superconductors have not been investigated sufficiently. In an early paper by Boiko et al [10] it was reported that the critical temperatures of some Tl-based superconductors either increase or decrease and the normalstate resistances drastically increase or remain the same depending the compositions of the samples and the range of the γ irradiation dose. In a more recent paper Hamdan et al [11] state that the properties of the fluorine-containing Tl-1223 are very sensitive to γ irradiation.…”

Effect of Direct Transport Current and Heat Treatment on Resistive Properties of Bismuth-Based Ceramic High-Temperature Superconducting Oxides of Various Compositions

“…Bulk ceramic (and especially bismuth-based) HTS systems are convenient objects for this purpose, because they contain a wide range of various granules linked by weak bonds of different energies. Here, the energy and character of these bonds in a sample can be modified by changing its impurity composition, bulk density as well as by applying external magnetic, electrical, radiation fields, and various types of heat treatment [11][12][13][14][15][16][17][18][19][20]. On the other hand, the choice of such complex HTS compound as bismuth ceramics is justified by the fact that here -as distinct from yttrium compounds -the effect of thermo-magnetic prehistory (hysteresis phenomena) on the resistive transition is relatively insignificant at low transport current densities [2].…”

“…When the HTS materials are irradiated by various high-energy particles at low doses, T C also exhibits nonmonotonic behavior depending on irradiation dose [16][17][18][19][20]. A typical granular HTS sample contains unstable phases in the form of various weak Josephson links, and each of them responds differently to external factors [16].…”

“…Non-monotonic variations of T C and r in granular HTS samples are observed with the increase of either the irradiation doses or transport current. It is pertinent to note that the observed non-monotonic dependence of the critical parameters of HTS materials with the increase of radiation dose is related to a complex process of restructuring of weak intergranular bonds [17] often accompanied by a change in the charge state of bismuth, copper and lead atoms [18,19]. Moreover, the comparison shows that the nature of the curves of HTS critical transition temperature and normal resistance with increasing dose [18,20] or transport current in the heat-treated sample B is qualitatively the same.…”