Aluminium-containing nitrogen melilite phases
- Monash Univ., Victoria (Australia). Dept. of Materials Engineering
- Univ. of Newcastle upon Tyne (United Kingdom). Dept. of Mechanical, Materials, and Manufacturing Engineering
A significant solubility of Al in N-melilite phases (M) has been observed, and this results in the formation of a melilite solid solution (M{prime}{sub ss}) of general formula Ln{sub 2}Si{sub 3{minus}x}Al{sub x}O{sub 3 + x}N{sub 4{minus}x} (Ln = rare earth). Up to one Si can be replaced by Al without change of structure, and the M{prime} solid solution terminates at Ln{sub 2}Si{sub 2}AlO{sub 4}N{sub 3} in samarium SiAlON systems. M{prime}{sub ss} may appear as an intermediate phase during the sintering of SiAlONs, and its melting temperature is critical to the densification of the materials. For example, samarium M{prime}{sub ss} melts at a temperature lower than neodymium M{prime}{sub ss} and as a result, samarium oxide shows better densification behavior in the preparation of {alpha}-SiAlON ceramics than does neodymium oxide. Devitrification of M{prime}{sub ss} from an amorphous grain boundary phase occurs above 1500 C during post heat-treatment. The M{prime}{sub ss} is refractory and may offer better oxidation resistance than N-melilite because of the replacement of Al-O for Si-N in the structure. Therefore M{prime}{sub ss} is considered to be a most desirable grain boundary phase for {alpha} and {alpha}-{beta} SiAlON ceramics.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 142245
- Journal Information:
- Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 1 Vol. 77; ISSN 0002-7820; ISSN JACTAW
- Country of Publication:
- United States
- Language:
- English
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