Electromagnetic and microstructural properties of bulk bicrystal grain boundaries in Bi₂Sr₂CaCu₂O_8+δ superconductors

We present systematic studies of electromagnetic and microstructural properties of bulk Bi₂Sr₂CaCu₂O_8+δ (Bi2212) bicrystals having synthetic [001] twist or naturally-grown [100] tilt boundaries. We find that [001] twist boundaries in as-prepared bicrystals, regardless of twist angles, conduct virtually the same critical current I_c as the constituent single crystals. We also irradiated some of the [001] twist bicrystals with 2.2 GeV Auions, and found that the [001] twist grain boundaries carry significantly less critical current than the irradiated single crystals in magnetic field. For naturally grown [100] tilt boundaries, we find a general T_c depression by several degrees at the grain boundary. Strong coupling behavior was observed in several high angle tilt grain boundaries below the grain boundary T_c^Gb.