Suppression of viscous grain-boundary sliding in a dilute SiAlON ceramic

Journal Article · Mon Sep 01 04:00:00 EDT 1997 · Journal of the American Ceramic Society

OSTI ID:554021

Pezzotti, G ^[1]; Kleebe, H J ^[2]; Ota, K ^[3]; Yabuta, Kazuya ^[4]

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1. Kyoto Inst. of Tech. (Japan). Dept. of Materials
2. Univ. Bayreuth (Germany). Inst. fuer Materialforschung
3. Osaka Univ. (Japan). Inst. of Scientific and Industrial Research
4. NKK Corp., Kawasaki (Japan). Materials and Processing Research Center

Aluminum nitride (AlN) and alumina (Al{sub 2}O{sub 3}) additives were blended into a high-purity silicon nitride (Si{sub 3}N{sub 4}) powder, and optimized processing conditions were applied for promoting a sintering process, which was shown to partly remove the amorphous silica-rich (SiO{sub 2}-rich) remains from grain boundaries. Such an approach led to the formation of a dilute SiAlON structure. The microstructure of the obtained SiAlON material consisted of two distinct types of matrix phases, namely, a main network of equiaxed (dilute) {beta}-SiAlON grains, with a minor fraction of (oxygen-rich) acicular O{prime}-SiAlON grains. As a consequence of the resulting solid solution of aluminum plus oxygen in the Si{sub 3}N{sub 4} lattice, many grain boundaries were free from any amorphous interlayer, as revealed by high-resolution electron microscopy (HREM) observation. Other than some boundaries that were still wetted, small amounts of residual glass were noted at dome triple-grain pockets. Internal-friction data that were collected up to very high temperatures showed that, in the present SiAlON material, no anelastic relaxation peak was monitored. Thus, viscous sliding along grain boundaries was inhibited. In addition, the partial elimination of the amorphous SiO{sub 2} film also implied that no continuous path for oxygen diffusion was available along grain boundaries. Because of this important circumstance and despite the possible softening effect due to solid solution, the viscoelastic (background) component of the internal-friction data shifted toward higher temperatures and the creep resistance of the material was improved.

• OSTI ID: 554021
• Journal Information: Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 9 Vol. 80; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
DEFORMATION
GRAIN BOUNDARIES
INTERNAL FRICTION
MICROSTRUCTURE
SILICON NITRIDES
SILICON OXIDES
SOLID SOLUTIONS
STRESSES
TEMPERATURE DEPENDENCE