High temperature strength of silicon nitride ceramics with ytterbium silicon oxynitride
- National Institute for Research in Inorganic Materials, 1-1, Namiki, Tsukuba, Ibaraki, 305 (Japan)
- Materials and Structures Laboratory, Tokyo Institute of Technology, 4529, Nagatsuta, Midoriku, Yokohama, Kanagawa, 226 (Japan)
Silicon nitride ceramics with ytterbium silicon oxynitride (Yb{sub 4}Si{sub 2}O{sub 7}N{sub 2}) as secondary phase were fabricated by hot-pressing the powder mixtures, including 50.0 to 97.0 mol{percent} of silicon nitride with a mixture of Yb{sub 2}O{sub 3} and SiO{sub 2} (Yb{sub 2}O{sub 3}/SiO{sub 2}=4). Sinterability of the materials with Yb{sub 2}O{sub 3} was higher than that with Y{sub 2}O{sub 3} in same composition of raw powder mixtures. High density materials was obtained under the condition of 50.0 to 89.1 mol{percent} of silicon nitride in raw powder mixtures. Mechanical properties of silicon nitride containing 97.6 mol{percent} of Si{sub 3}N{sub 4} and 2.4 mol{percent} of Yb{sub 4}Si{sub 2}O{sub 7}N{sub 2} were measured. Fracture toughness measured by indentation technique was 5.9 MPam{sup 1/2}. Bending strength at room temperature and at 1500{degree}C was 977 MPa and 484 MPa, respectively. The silicon nitride grains were consisted of highly elongated rod-like grains and thin needle-like grains. The Yb{sub 4}Si{sub 2}O{sub 7}N{sub 2} grains were crystallized at multigrain junctions and bonded close to Si{sub 3}N{sub 4} grains. High strength at high temperature is supposed to be based on the presence of crystalline Yb{sub 4}Si{sub 2}O{sub 7}N{sub 2} having high melting point. {copyright} {ital 1997 Materials Research Society.}
- OSTI ID:
- 450284
- Journal Information:
- Journal of Materials Research, Journal Name: Journal of Materials Research Journal Issue: 1 Vol. 12; ISSN JMREEE; ISSN 0884-2914
- Country of Publication:
- United States
- Language:
- English
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