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Characterization of Long Period Polytypoid Structures in The Al2O3-AlN System

Published online by Cambridge University Press:  28 February 2011

Kannan M. Krishnan ,
R.S. Rai ,
G. Thomas ,
N.D. Corbin  and
J.W. McCauley
Kannan M. Krishnan
Affiliation:
National Center for Electron Microscopy, Lawrence Berkeley Laboratory, University of California, Berkeley, CA 94720
R.S. Rai
Affiliation:
National Center for Electron Microscopy, Lawrence Berkeley Laboratory, University of California, Berkeley, CA 94720
G. Thomas
Affiliation:
National Center for Electron Microscopy, Lawrence Berkeley Laboratory, University of California, Berkeley, CA 94720
N.D. Corbin
Affiliation:
Army Mechanics and Materials Research Center, Watertown, MA 02172
J.W. McCauley
Affiliation:
Army Mechanics and Materials Research Center, Watertown, MA 02172
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Abstract

Long period polytypoid structures observed along the pseudobinary Al2O3-AlN composition join at a composition of 95 mol% A1N have been investigated by convergent beam electron diffraction and lattice imaging. Two new long period structures, 32H (Ramsdell notation) and 16H with c-periodicities of 8.3 nm and 4.07 nm respectively, have been independently identified by these two techniques. However, the 32H polytypoid was sometimes found to be intergrown with faulted 27R long period structure of periodicity 7.2 nm. Further, it has been shown that the 32H polytypoid is stabilized by local compositional fluctuations during the sintering process.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 60: Symposium L – Defect Properties and Processing of High-Technology Nonmetallic Materials , 1985 , 211
Copyright
Copyright © Materials Research Society 1986

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