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Fabrication and Properties of Si3N4 with Rare Earth Apatite Grain Boundary Phases

Published online by Cambridge University Press:  25 February 2011

Terry N. Tiegs ,
Stephen D. Nunn ,
Kristin L. Ploetz ,
Paul A. Menchoffer  and
Claudia A. Walls
Terry N. Tiegs
Affiliation:
Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6087
Stephen D. Nunn
Affiliation:
Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6087
Kristin L. Ploetz
Affiliation:
Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6087
Paul A. Menchoffer
Affiliation:
Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6087
Claudia A. Walls
Affiliation:
Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6087
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Abstract

The rare earth-oxide and nitride apatites were examined as grain boundary phases in silicon nitride to assess their potential for developing high toughness materials using gas-pressuresintering. Densification was dependent on the quantity of additives used with high densities achieved at equivalent oxygen contents of ∼8%. Fracture toughnesses (KIc) up to 8-10 MPa√m were obtained for some compositions. Ambient temperature flexural strengths were in the range of 400-720 MPa; however, the strengths atelevated temperatures (1200ºC) were reduced from these values.

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References

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