Microstructural studies on YBCO film bicrystals with large single facetgrain boundaries grown by liquid phase epitaxy

Abstract

In order to understand the intrinsic dependence of intergranularJc on the misorientation angle, a large, single-faceted grain boundary (GB)that is atomically smooth is necessary. Growth of YBCO film on MgO bicrystalsubstrates by liquid phase epitaxy (LPE) was applied to obtain largesingle-faceted GBs. Plan-view and cross sectional TEM observations confirmedthat the GBs are straight and a single facet with 10-30 µm dimension can beeasily found. High-resolution electron microscopic studies on these GBs showedthat GBs with misorientation angles of 4°, 8°, 12°,16° and 45° are single facets at the atomic scale, but 24°and 36° GBs are faceted at a scale, of a few nanometres. Shearstructures at stacking faults observed at asymmetric low-angle GB may resultin a Cu-rich GBs, so the stacking fault becomes insulting and is a strongbarrier for current flow. A possible relationship between the dependence ofJc on misorientation angles and microstructures are discussed for LPEbicrystals.