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Densification Behavior and Properties of Y 2 O 3 ‐Containing α‐SiAlON‐Based Composites
Author(s) -
Bandyopadhyay Siddharta,
Hoffmann Michael J.,
Petzow Günter
Publication year - 1996
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.1151-2916.1996.tb08762.x
Subject(s) - melilite , sialon , materials science , composite material , phase diagram , phase (matter) , yttrium , crystallization , ceramic , chemical engineering , metallurgy , chemistry , oxide , spinel , organic chemistry , engineering
Different SiAION composites based on α′‐SiAION are investigated, with respect to the phase relationships, densification behavior, and mechanical properties. The compositions are located on a phase‐diagram line parallel to the Si 3 N 4 ‐Y 2 O 3 9AIN compound in the Si 3 N 4 ‐SiO 2 ‐AlN‐Al 2 O 3 ‐Y 2 O 3 ‐YN system. Analysis of the reaction sequences shows that the formation of the composites is associated with the transient appearance of Y 4 A1 2 O 9 (YAM), yttrium‐aluminum‐garnet (YAG), melilite, and a nitrogen‐rich liquid phase. The small shift of compositions on the Si 3 N 4 ‐Y 2 O 3 ‐9AIN compound phase‐diagram line toward the Al 2 O 3 ‐rich side offers the advantage of a higher sinterability and the removal of the melilite phase from a wide range of compositions containing α′‐SiAlON and polytypes. The α′/β′‐SiAlON composites show better mechanical properties in comparison to pure α′‐SiAlON and composites of α′‐SiAION and polytypes. A post‐heat‐treatment causes the crystallization of YAG as a grain‐boundary phase and leads to excellent strength retention up to temperatures of 1350°C.