The origins of high values of the critical current density in the Bi2Sr2Can−1CunOx system: high-Tc superconducting pathways at low angle tilt boundaries

Review: grain boundary faceting–roughening phenomena

“…Below h = 20°, the GB contains the segments of perfect contact of abutting grains forming the high-T c ''pathways'' crossing the boundary plane. They are separated by dislocation cores with low T c [219,[225][226][227][228][229]. One can say to a first approximation, that thereafter a continuous insulating layer of 2-3 nm will lead to a constant attenuation of the supercurrent.…”

Structure of grain boundaries: Correlation to supercurrent transport in textured Bi2Sr2Can−1CunOx bulk material

“…35 High J c anisotropy along different sample directions and for different field directions was observed in our CRT sample. 17,18 Although the misorientation itself can lower the critical current, besides the crystallographic effect of high angle itself, the microstructure shows that there is likely to be an additional reason. 1) is 30 times higher than the critical current density along the Z direction (the common c-axis), 36 which is in qualitative agreement with the behavior of the (2212) single crystal.…”

“…1,2 In the Bi 2 Sr 2 Ca n-1 Cu n O x system the critical current density, J c , can be particularly high for textured samples [3][4][5][6][7] that are well aligned with the c-axis perpendicular to the direction of current flow compared with more randomly oriented polycrystal samples. [16][17][18] The form of the associated local compositional and structural changes for low-and high-angle tilt boundaries (with or without associated twist components) is completely different from that observed in the YBa 2 Cu 3 O 7-d system and could significantly affect the supercurrent transport. 5,9 Thus understanding and controlling the grain boundary behavior is a central issue in the technological development of high T c superconductors.…”

“…The structural changes along the boundary can be described using the notation ͕͑n, n 0 ͒͞m͖, 16,18 in which n and n′ denote the value of n (1, 2, 3 . .…”

“…It was reported that the J c values in thin films of YBaCuO are quite sensitive to the misorientation between adjacent grains separated by a grain boundary, and decrease drastically when the angle of the misorientation exceeds about 10 ± . [11][12][13][14][15][16][17][18] Our previous work for this system has demonstrated that the grain boundaries exhibit unusual changes in local stoichiometry. 8,9 It has been demonstrated that, the worse the c-axis alignment, the more rapidly J c falls off as a function of applied magnetic field.…”