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Oxidation Behavior of Rare‐Earth Disilicate–Silicon Nitride Ceramics
Author(s) -
Cinibulk Michael K.,
Thomas Gareth,
Johnson Sylvia M.
Publication year - 1992
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.1151-2916.1992.tb04463.x
Subject(s) - devitrification , microstructure , materials science , ceramic , amorphous solid , silicon nitride , impurity , silicon , mineralogy , silicate , chemical engineering , crystallography , crystallization , metallurgy , chemistry , organic chemistry , engineering
The oxidation behavior and microstructure of the oxidized surfaces of RE 2 Si 2 O 7 –Si 3 N 4 ceramics were investigated. The high oxidation resistance of these materials at 1400°C is attributed to the minimization of amorphous phases via devitrification to disilicates that are in equilibrium with SiO 2 , the oxidation product of Si 3 N 4 . Crystals of RE 2 Si 2 O 7 grew out of the surface silicate in prefered orientations that were dictated by crystal structure. The morphology of the microstructure of the oxidized surfaces was shown to be partially dependent on the concentration of impurities; the presence of Ca was found to coincide with the growth of Gd 2 Si 2 O 7 and Dy 2 Si 2 O 7 crystals with high aspect ratios.