AC and DC transport current in melt-grown YBCO

It has been suggested that the transport J/sub c/ in multigrain samples of bulk YBCO is limited by the intergrain links. The authors report on preliminary measurements of intergrain currents. The intergrain critical currents in melt-grown YBCO do not appear to be as sensitive to the precise crystallographic alignment of adjacent grains as has been reported for thin films. The measured critical current of similar grain boundaries varies widely, between 15000 A/cm/sup 2/ and 200 A/cm/sup 2/ for adjacent boundaries in the same sample. Preliminary results support the conclusions of S.E. Babcock et al. (Nature, vol.347, p.167, 1990), who found weak-link-free behavior in some high-angle boundaries between bulk crystals.