Polytypism in Magnesium Sialon
The crystallography and morphology of the 12H and 21R polytypes in a magnesium sialon (Mg1. 86 Si 1-67Al2.4703.19N3.81)have been investigated by lattice fringe imaging and electron diffraction, Intergrowths of the two poly types occur, but since they have different crystal sizes, mismatch strains are introduced which may have a detrimental effect on mechanical properties of the material. It is concluded that careful control of the starting powders and long hotpressing times will be necessary to avoid the formation of these strained intergrowths.
KeywordsElectron Diffraction Pattern Close Packed Plane Mismatch Strain Dark Fringe Close Packed Layer
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