TRANSPORT-PROPERTIES OF AN ENGINEERED [001]-TILT SERIES IN BULK YBA2CU3O7-X BICRYSTALS

Single grain boundaries (GB's) of an engineered [001] tilt series of b ulk YBa2Cu3O7-x (YBCO) bicrystals were electrically characterized to p robe the intrinsic and extrinsic factors influencing GB properties of bulk melt-processed (MP) YBCO. The bicrystal series ranged from 1.5 de grees to 45 degrees misorientation angle and displayed tendencies simi lar to those of thin film GB's at 77 K in self-field. Subtle differenc es between thin film and bulk GB transport behavior that were observed may be attributed to the thin film substrate. The dependence of norma l-state resistance (R(n)) at 77 K on the [001] tilt angle has been not ed. An anticorrelation between R(n) and critical current (I-c) exists such that the product, I(c)R(n), of each bicrystal from 10 degrees to 45 degrees falls within a narrow band of 10 to 20 mu V. Such a narrow characteristic voltage range suggests highly reproducible growth condi tions. It is also reasonable to suggest that naturally grown boundarie s in bulk MP YBCO have more uniform GB character than their thin film counterparts. This advantageous growth technique allows us to further probe the role of the GB plane in influencing transport properties.