Influence of the Rare-Earth Element on the Mechanical Properties of RE–Mg-Bearing Silicon Nitride

Authors

  • Raphaëlle L. Satet,

    Corresponding author
    1. Institute for Ceramics in Mechanical Engineering, University of Karlsruhe, D-76131 Karlsruhe, Germany
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    • *Member, American Ceramic Society.

  • Michael J. Hoffmann

    1. Institute for Ceramics in Mechanical Engineering, University of Karlsruhe, D-76131 Karlsruhe, Germany
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    • *Member, American Ceramic Society.


  • M. Cinibulk—contributing editor

  • This work was supported by the European Community “Growth” Program under the NANOAM contract G5RD-CT2001-00586.

†Author to whom correspondence should be addressed. e-mail: raphaelle.satat@ikm.uka.de

Abstract

Silicon nitride bulk ceramics with varying compositions of the grain boundary phase but similar grain sizes were developed, which allows to analyze the influence of the grain boundary chemistry on mechanical properties. Micrographs of the crack path reveal a much weaker interface when the rare-earth element in the grain boundary phase changes from a small to a large rare-earth cation (RE3+). Room temperature measurements of toughness and bending strength show that weaker grain boundaries result in a higher toughness, but in a decreased strength of the bulk material. This investigation demonstrates that the mechanical behavior of silicon nitride can be readily tuned by chemical composition changes of the grain boundary phase, but that a compromise between toughness and strength has to be found when designing the material.

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