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Nucleation and Abnormal Grain Growth of Alpha-A12O3 in Gamma-Alumina Matrix

Published online by Cambridge University Press:  15 February 2011

T. C. Chou  and
T. G. Nieh
T. C. Chou
Affiliation:
Lockheed Missiles and Space Company, Research and Development Division, O/93-10, B/204, Palo Alto, CA 94304
T. G. Nieh
Affiliation:
Lockheed Missiles and Space Company, Research and Development Division, O/93-10, B/204, Palo Alto, CA 94304
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Abstract

The microstructures of reactive sputter-deposited alumina films have been studied by transmission electron microscopy. The as-deposited films contained γ-A12O3 phase in an amorphous alumina matrix. Annealing of the films at 1200° C for 2 h resulted in nucleation and concurrent anomalous grain growth of α-A12O3 in a polycrystaUine γ-Al2O3 matrix which exhibited a layered microstructure and was strongly textured along [001]. The grain sizes of α-A12O3 varied from 3 to 20 μm, while the average grain size of γ-A12O3 was only about 50 nm. It appears that the nucleation kinetics of a-A12O3 was slow. As a result, the abnormal grain growth of α-A12O3 proceeded by consuming surrounding γ-Al2O3 grains. An atomic model is presented to explain the origin of layered structure in γ-A12O3. The nucleation mechanism of a-A12O3 in γ-alumina matrix is suggested. Orientation relationships between γ- and α-A12O3 are reported. The anomalous grain growth of α- A12O3 is discussed in terms of γ/α interface boundary migration.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 230: Symposium R – Phase Transformation Kinetics in Thin Films , 1991 , 345
Copyright
Copyright © Materials Research Society 1992

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