SEM investigation of the critical current degradation onset in BSCCO-2223 multifilamentary tapes submitted to bending

Abstract

The applicability of superconducting tapes is evaluated employing the definition of an irreversibility strain irr , attained at a critical current density J c of 98% of its initial value. Before reaching this limit, the J c decreases slowly. In order to determine the microstructural changes responsible for this behaviour, we investigated the mechanical response of 19-filament BSSCCO-Ag tapes with different ceramic microstructures, when bent without exceeding irr . After chemically removing a rectangular-shaped area of the silver sheath to expose the ceramic filaments, the samples were subjected to three-point bending inside an SEM chamber. Thus, we were able to follow the microstructural changes produced by the formation and propagation of cracks at the same time that we recorded on a PC the force versus deflection curves. We identified three different regions representing the response of the tapes to increasing bending. After the elastic region, the pre-existing microstructural faults determined the plastic behaviour. At higher deflections, we measured several stress drops coincident with the observation of micro-cracks that grew slowly across the filaments. Twin samples were employed to control the critical current density decay as a function of the bending deflection introduced at ambient temperature. We investigated the correlation between the bending induced defects and the critical current degradation.

Investigation of Structural and Superconducting Properties of Cr Added Bi-2212 Superconducting Ceramics

“…Several techniques [6][7][8][9][10][11][12][13][14] have widely been used to improve their superconducting properties for years. Rare-earth addition and substitution are the most commonly used techniques [15][16][17][18].…”

Investigation of Gd Addition Added on Magnetic and Structural Properties of Bi1.8Pb0.35Sr1.9Ca2.1Cu3Gd x O y Superconductors by ac Susceptibility

“…Figure 1, displaying the ac susceptibilities (χ and χ ) versus temperature graphs, reveals that onset temperatures (T on c ) were observed to be about 110 K for Gd0, 89 K for Gd1, 81 K for Gd2, 76 K for Gd3, 56 K for Gd4 and 40 K for Gd5 sample respectively. On the other hand, the loss peak temperatures (T p ), representing the full flux penetration in the out of phase component of the samples, are noted to be about 105 (93) K for Gd0, 84 (71) K for Gd1, 77 (66) K for Gd2, 71 (59) K for Gd3, 44 (33) K for Gd4 and 30 (19) K for Gd5 at 270 (1352) A/m ac field, respectively.…”

“…For years, researchers have tried to improve their superconducting properties by using several techniques [12][13][14][15][16][17][18][19][20]. The improvement of the critical current density means the enhancement of trapped flux in the superconductor material [21,22] and single domain structure [23,24].…”

Effect of Mn Addition on Structural and Superconducting Properties of (Bi, Pb)-2223 Superconducting Ceramics

“…Since discovery of the Bi-based superconductor ceramics, researchers have tried to improve their structural, mechanical and superconducting properties by using several techniques [17][18][19][20][21][22][23][24][25]. Especially, the chemical doping in the superconductor materials plays a major role to improve these properties [26].…”