The influence of the bulk density on the intergranular superconducting properties of YBa2Cu3−xFexOy (0≤x≤0.01) ceramics

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

“…Review of recent works has evidenced the importance of penetration of the self magnetic field of the transport current (I) in the ceramic high-temperature superconducting (HTS) materials [1][2][3][4][5]. The interest in such investigations is caused by the need for high critical currents determined by the structural quality of the HTS samples [1][2][3][4][5][6], which is dependent on the impurity content, geometrical dimensions of the samples as well as on the thermal treatment conditions [7][8][9][10][11][12][13]. When at least two superconducting phases are presented in bismuth samples, the analysis of temperature dependence of resistivity r (T) is much more complicated [5][6][7][8][9][10].…”

“…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].…”

“…And at the same J= 0.064 A/cm, T C 0.5 = 94 K for sample B exceeds that for sample A (T C 0.5 = 83 К) due to the fact that for sample B the superconducting phase 2212 predominates [6]. Besides, the reason for the observed differences in the samples properties is also related to different sample densities and the volume fraction of superconducting and non-superconducting phases [6][7][8][9][10][11][12][13][14]. The ratio of these phases varies non-monotonically depending on Sr/Ca ratio in the samples and their heat treatment regimes [6,9].…”