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Equilibrium Shape of Internal Cavities in Ruby and the Effect of Surface Energy Anisotropy on the Equilibrium Shape
Author(s) -
Choi JungHae,
Kim DohYeon,
Hockey Bernard J.,
Wiederhorn Sheldon M.,
Blendell John E.,
Handwerker Carol A.
Publication year - 2002
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2002.tb00362.x
Subject(s) - sapphire , surface energy , equiaxed crystals , anisotropy , materials science , annealing (glass) , facet (psychology) , surface (topology) , indentation , basal plane , ion , hillock , crystallography , condensed matter physics , geometry , optics , chemistry , physics , composite material , microstructure , psychology , social psychology , laser , mathematics , personality , organic chemistry , big five personality traits
Cavities formed in ruby (99.46Al 2 O 3 ·0.54Cr 2 O 3 ) by the healing and annealing of indentation cracks at 1600°C are more equiaxed than similar cavities in sapphire. Surface energies for the observed facet planes (R, S, and A) relative to the surface energy of the basal plane, C , were γ A/C = 1.00 ± 0.03, γ R/C = 1.05 ± 0.07, and γ S/C = 1.02 ± 0.04, with the uncertainty representing 95% confidence limits. Thus, the surface energies of all observed facets were statistically indistinguishable. Unlike sapphire, P‐plane facets were not observed. The substantial rounding of the cavities in ruby indicated that portions of the Wulff shape were above the roughening transition temperature. Thus, even though Cr 2 O 3 and Al 2 O 3 form ideal solutions, Cr 3+ ions are sufficiently surface active to modify the relative free energy of the surfaces.