Densification Behavior and Properties of Y2O3-Containing α-SiAlON-Based Composites |
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Authors: | Siddharta Bandyopadhyay Michael J Hoffmann † Günter Petzow |
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Affiliation: | Max-Planck-Institut für Metallforschung, Institut für Werkstoffwissenschaft, Pulvermetallurgisches Laboratorium, D-70569 Stuttgart, Germany |
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Abstract: | 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 Si3N4-Y2O3 9AIN compound in the Si3N4-SiO2-AlN-Al2O3-Y2O3-YN system. Analysis of the reaction sequences shows that the formation of the composites is associated with the transient appearance of Y4A12O9 (YAM), yttrium-aluminum-garnet (YAG), melilite, and a nitrogen-rich liquid phase. The small shift of compositions on the Si3N4-Y2O3-9AIN compound phase-diagram line toward the Al2O3-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. |
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