Microstructure of (Hg,Re)-1212 grain boundary junctions grown on STO bicrystal substrates

Microstructure of Re-doped Hg-1212 thin film grain boundaries (GBs) fabrica ted by a two-step process on SrTiO3 bicrystal substrates with 45 degrees an d 24 degrees tilt angles has been examined by transmission electron microsc opy observation and compared with that of YBa2Cu3O7-delta. It was revealed that the GBs of the (Hg,Re)-1212 film are wavy with many facets, of which s ize is a few nanometers. Both symmetric and asymmetric facets are found in the 'symmetrically' tilted 24 degrees boundaries. Moreover, the facets in t he GBs are mainly asymmetric in the 45 degrees GB. There are some regions o n the GBs containing many precipitates, which may cause inhomogeneous junct ion transport properties. (C) 2001 Elsevier Science B.V. All rights reserve d.