Faceting, dislocation structure, and various scales of heterogeneity in a YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} low-angle [001] tilt boundary
- Materials Science and Engineering and Applied Superconductivity Center, University of Wisconsin- Madison, Madison, Wisconsin 53706-1687 (United States)
- Ceramics Division, NIST, Gaithersburg, Maryland 20899 (United States)
The grain boundary topography and grain boundary dislocation network structure of a 6{degree} [001] bicrystal of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} were studied using diffraction-contrast transmission electron microscopy (TEM). Saw-tooth-shaped arrays of facets composed of facets with lengths of a few tens of nanometers were observed in each of two widely separated sections of the boundary. The facet planes were {l_brace}110{r_brace}, {l_brace}310{r_brace}, and {l_brace}22{bar 1}{r_brace}. Further subfaceting of the (130) facets into a smaller-scale (a few nanometers) saw-tooth configuration of (010) and (110) facets produced a hierarchy of facets in at least one boundary section. The dislocation content observed in each type of facet agreed well with Frank{close_quote}s formula. However, the dislocations within individual facets frequently were inhomogeneously distributed, contrasting the picture of evenly spaced dislocations that is derived for boundaries of infinite extent. Certain types of dislocations repeatedly were grouped near the facet centers and ends. Well-separated partial dislocations frequently were observed near the facet midsections, but not near the facet junctions. Extended ({approximately}30 nm) strain contrast was observed at all of the facet junctions formed by facets with dimensions on the order of tens of nanometers. This long-range strain may be due to the finite extent of the individual facets. These results all suggest that structural inhomogeneities occur on various length scales ranging from macroscopic to just a few nanometers. Such structural heterogeneity is consistent with the electrical heterogeneity that is indicated for many YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} grain boundaries. {copyright} {ital 1996 Materials Research Society.}
- OSTI ID:
- 285861
- Journal Information:
- Journal of Materials Research, Vol. 11, Issue 6; Other Information: PBD: Jun 1996
- Country of Publication:
- United States
- Language:
- English
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