The extent of chemical redistribution into crystals which bounded whisker/matrix interfaces and matrix grain boundaries, and the lateral continuity of the distributions, were investigated by means of analytical electron microscopy and were compared with the structural widths which were determined by means of high-resolution transmission electron microscopy. The extent of redistribution into the bounding crystals (defined as the chemical width) was between 10 and 120 times the structural width. This ratio was greater for the grain boundaries than for the interfaces. Moreover, the chemical distributions were laterally discontinuous at interfaces, but were continuous at grain boundaries. Oxides such as Y2O3 and Al2O3 were the main components to be redistributed. The distributions were studied by means of position-resolved electron energy loss spectroscopic and Z-contrast scanning transmission electron microscopic methods. Microstructural observations indicated that the chemical widths resulted from solid-state diffusion into the bounding crystals, and that lateral discontinuities in the distributions resulted from Gibbs-Thompson solution effects of the whisker surfaces at interfaces.

K.D.Chowdhury, R.W.Carpenter, W.Braue, J.Liu, H.Ma: Journal of the American Ceramic Society, 1995, 78[10], 2579-92