Origin and growth kinetics of platelike abnormal grains in liquid-phase-sintered alumina

Journal Article · Sun Jul 01 04:00:00 EDT 1990 · Journal of the American Ceramic Society; (USA)

DOI:https://doi.org/10.1111/j.1151-2916.1990.tb05271.x· OSTI ID:6072323

Song, H; Coble, R L ^[1]

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1. Massachusetts Inst. of Tech., Cambridge, MA (USA). Dept. of Materials Science and Engineering

The grain-growth behavior of Al{sub 2}O{sub 3} compacts with small contents ({le}10 wt%) of various liquid-forming dopants was studied. Equiaxed and/or elongated grains were observed for the following dopants: MgO, CaO, SiO{sub 2}, or CaO + TiO{sub 2}. The platelike grains, defined as the abnormal grains larger than 100 {mu}m with an aspect ratio {ge}5 and with flat boundaries along the long axis, were observed when the boundaries were wet with the liquid phase and the codoping satisfied two conditions of size and valence. These dopings were Na{sub 2}O + SiO{sub 2}, CaO + SiO{sub 2}, SrO + SiO{sub 2}, or BaO + SiO{sub 2}. However, an addition of MgO to the Al{sub 2},O{sub 3} doped with CaO + SiO{sub 2} resulted in the change of grain shape from platelike to equiaxial. Equiaxed grains were also observed for the MgO + SiO{sub 2} doping, indicating that two conditions were necessary but not sufficient to develop the platelike grains. The fast growth rate of the platelike grains is explained by an increased interfacial reaction rate due to the codopants.

• OSTI ID: 6072323
• Journal Information: Journal of the American Ceramic Society; (USA), Journal Name: Journal of the American Ceramic Society; (USA) Vol. 73:7; ISSN 0002-7820; ISSN JACTA
• Country of Publication: United States
• Language: English

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36 MATERIALS SCIENCE
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ALUMINIUM COMPOUNDS
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CALCIUM COMPOUNDS
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PARTICLE SIZE
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