Transport properties of Bi2Sr2CaCu2O8+delta bicrystals with [100] tilt grain boundaries

We have successfully isolated more than a dozen of naturally-grown [100] ti lt Bi2Sr2CaCu2O8+delta (Bi-2212) bicrystals for the study of the transport properties of the grain boundary. These bicrystals contain a single clean [ 100] nonbasal-plane-faced tilt grain boundary with various degrees of misor ientation. Systematic transport measurements of these grain boundaries were performed in a wide range of temperature and magnetic field by measuring t he resistance and the current-voltage characteristics for both single cryst als and grain boundaries simultaneously. In addition, the microstructures o f the grain boundaries in some of these bicrystals were studied by both con ventional TEM and high-resolution electron microscopy (HREM). We found that almost all these [100] non-basal-plane-faced tilt grain boundary had a T-c depression (about 6 K to 9 K) as compared to their constituent single crys tals. However, at low temperatures, these grain boundaries do not behavior like weak-links. In fact, several high angle tilt grain boundaries can carr y the same amount of critical current as their constituent single crystals. Our results suggest that the effect of misorientation angle on the grain-b oundary coupling strength in this type of Bi-2212 grain boundary is much le ss predominant than that in the same type of grain boundary of YBa2Cu3O7-de lta (YBCO).