Bibliographic Citation
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| Title | Crystallization of pseudo-orthorhombic anorthite on basal sapphire |
| Creator/Author | Mallamaci, M.P. ; Carter, C.B. [Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Chemical Engineering and Materials Science] |
| Publication Date | 1999 Jan 01 |
| OSTI Identifier | OSTI ID: 316019 |
| DOE Contract Number | FG02-92ER45465 |
| Other Number(s) | Journal ID: JACTAW; ISSN 0002-7820; TRN: TRN: IM9908%%99 |
| Resource Type | Journal Article |
| Resource Relation | Journal Name: Journal of the American Ceramic Society; Journal Volume: 82; Journal Issue: 1; Other Information: PBD: Jan 1999 |
| Sponsoring Org | USDOE, Washington, DC (United States) |
| Subject | 36 MATERIALS SCIENCE; ENERGY BEAM DEPOSITION; CRYSTALLIZATION; ANORTHITE; FILMS; GLASS; LASERS; SAPPHIRE; ELECTRON MICROSCOPY; DISLOCATIONS |
| Description/Abstract | Anorthite-glass films were grown on basal Al{sub 2}O{sub 3} substrates using pulsed-laser deposition. The substrates were cleaned and annealed in air at 1400 C to produce crystallographically flat (0001) terraces. The films were deposited in an oxidizing environment. X-ray microanalysis confirmed the composition of the glass films to be close to that of anorthite (CaO{center_dot}Al{sup 2}O{sub 3}{center_dot}2SiO{sub 2}). Although anorthite usually has triclinic symmetry, subsequent crystallization of these films in air at 1200 C resulted in the formation of pseudo-orthorhombic CaAl{sub 2}Si{sub 2}O{sub 8} (o-anorthite), a known metastable form of the mineral. Microstructural characterization was performed using visible-light microscopy, scanning electron microscopy, and transmission electron microscopy. The films dewetted the substrate either before or after crystallization to form o-anorthite islands which had strong orientation relationships to the Al{sub 2}O{sub 3} substrate. The epitaxy of the o-anorthite islands was accompanied by a small lattice mismatch parallel to the substrate plane. The formation of three orientational variants is consistent with the symmetry of the basal Al{sup 2}O{sub 3} surface. The dislocation network observed at the o-anorthite/Al{sub 2}O{sub 3} interface indicates that nucleation and growth of the anorthite occurs directly on the substrate surface without an intervening interfacial amorphous layer. The study of anorthite-glass films is important because they are present in liquid-phase-sintered Al{sub 2}O{sub 3}, and may be devitrified by postsintering heat treatments. |
| Country of Publication | United States |
| Language | English |
| Format | Medium: X; Size: pp. 33-42 |
| System Entry Date | 2009 Dec 16 |
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