Duplex {alpha},{beta}-sialon ceramics stabilized by dysprosium and samarium
- Univ. of Stockholm (Sweden)
- Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Physics
- Zhejiang Univ., Hangzhou (China). Dept. of Materials Science and Engineering
Duplex {alpha},{beta}-sialon ceramics with a minimum volume fraction of residual intergranular glass have been prepared using Dy or Sm as the {alpha}-sialon stabilizing element. These microstructures contained high aspect ratio {beta}-sialon grains homogeneously distributed in an {alpha}-sialon matrix. A number of the larger {alpha}-sialon grains contained dislocations and showed a core/shell structure. Dy gave an {alpha}-sialon which was stable over a wide temperature range (1,350-1,800 C) for long holding times, while the use of Sm resulted in less stable {alpha}-sialon structures at medium temperatures (1,450 C) and the formation of melilite, R{sub 2}Si{sub 3{minus}x}Al{sub x}O{sub 3+x}N{sub 4{minus}x}, {beta}-sialon, and the 21R sialon polytype during prolonged heating. High {alpha}-phase contents gave a very high hardness (H{sub V10} {approx} 22 GPa) but a comparatively low indentation fracture toughness (around 4.4 MPa{center_dot}m{sup 1/2}). Duplex sialons fabricated from powder mixtures corresponding to an {alpha}-to-{beta} sialon ratio of around 50:50 resulted in a sialon material with a favorable combination of high hardness (around 22 GPa) and increased toughness (to around 5.5 MPa{center_dot}m{sup 1/2}).
- OSTI ID:
- 483654
- Journal Information:
- Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 2 Vol. 80; ISSN 0002-7820; ISSN JACTAW
- Country of Publication:
- United States
- Language:
- English
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