Chemical Vapor Deposition of Polycrystalline Al2O3 |
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Authors: | PHILIP WONG McDONALD ROBINSON |
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Affiliation: | Army Materials and Mechanics Research Center, Watertown, Massachusetts 02172 |
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Abstract: | Polycrystalline Al2O3 was chemically vapor-deposited onto sintered Al2O3 substrates by reaction of AlCl3 with (1) H2O, (2) CO:H2, and (3) O2 at 1000° and 1500°C and 0.5 and 5.0 torr. Although the thermodynamics of all these reactions predict the formation of solid Al2O3, the deposition rate of the first reaction was considerably greater than that of the second. The third reaction was so slow that no measurable deposit was formed in 6 h at 1500°C. Formation of dense deposits of α-Al2O3 was favored by increasing temperature and decreasing pressure. Microstructural examination of the dense deposits showed long columnar grains, the largest of which extended through the deposit from the substrate to the surface. |
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