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Influence of Secondary Phase Chemistry on Grain-Boundary Film Thickness in Silicon-Nitride

Kleebe, H. J.; Hoffmann, M. J.; Ruhle, M.


The microstructures of liquid-phase sintered Si3N4 materials were
investigated using analytical and high-resolution electron microscopy
(AEM, HREM). Microstructural characterization was performed with
emphasis on interfacial grain-boundary structure and chemistry. All
materials investigated consist of large elongated beta-Si3N4 grains
embedded in a globular fine-grained beta-Si3N4 matrix. Amorphous
secondary phases are observed mainly at three- and four-grain junctions
owing to the liquid-phase sintering process involved during
densification. Upon postsintering heat treatment crystalline secondary
phases form at triple grain regions. However, complete crystallization
cannot be achieved. All grains are covered with a thin amorphous
intergranular film at both homo-phase and heterophase boundaries. In
addition, the film thickness of heterophase boundaries is always
greater than homo-phase boundary films. The presence of amorphous
intergranular films profoundly affects the mechanical properties of
Si3N4-based ceramics at room and elevated temperatures. Therefore, a
control of these films is most desirable. Si3N4 materials with
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Zugehörige Institution(en) am KIT Fakultät für Maschinenbau – Institut für Keramik im Maschinenbau (IKM)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 1992
Sprache Englisch
Identifikator ISSN: 0044-3093
KITopen-ID: 1000007796
Erschienen in Zeitschrift für Metallkunde
Verlag Carl Hanser Verlag
Band 83
Heft 8
Seiten 610-617
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