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Epitaxial growth phenomena

The aim of this study was to understand the fine structure of the alumina-zirconia inter-face as a foundation for better insight into the TGO-TBC adherence. Extensive TEM studies have been performed at MPI-MF on YSZ films grown on sapphire at UCSB, including both the structure of the columns and associated porosity, their texture and the orientation relation-ships with the substrate.

A significant finding has been that YSZ nucleates on sapphire with a strong out-of-plane epitaxy but otherwise in-plane randomness. This has provided substantial insight into the various mechanisms of evolutionary selection operating during growth, and the influence of the initial distribution of grain orientations on the column size. Concur-rent studies on the growth of YSZ on sapphire substrates containing a distribution of YSZ seeds prepared by precursor methods have shown that seed surfaces are less favourable for epitaxial growth. TEM analysis suggests that this is probably due to segregation of trace con-taminants to the surface.

Reported by

Max-Planck-Institut fur Metallforschung
Heisenbergstr. 3
D70569 Stuttgart
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