Formation and characteristics of silicon nitride-lithium aluminum silicate ceramics: I. Sintering and microstructure
- Max-Planck-Institut fuer Metallforschung, Stuttgart (West Germany)
Silicon nitride ceramics with the grain-boundary phase {beta}-eucryptite, LiAlSiO{sub 4}, or {beta}-spodumene, LiAlSi{sub 2}O{sub 6}, were produced by pressureless sintering {alpha}-Si{sub 3}N{sub 4}, SiO{sub 2}, and LiAlO{sub 2} powder mixtures at 1,300{degree} to 1,900{degree}C. The phase relations in the system Si{sub 3}N{sub 4}-LiAlO{sub 2}-SiO{sub 2} were investigated at 1,500{degree}C, showing the presence of an Si-Li-O rich liquid phase. During annealing at 900{degree} to 1,300{degree}C, {beta}-eucryptite precipitated when the sintering temperature was <1,700{degree}C, whereas {beta}-spodumene crystallized when it was >1,700{degree}C. Because of the low thermal expansion of {beta}-LiAlSiO{sub 4} and {beta}-LiAlSi{sub 2}O{sub 6} ({minus}6.3 {times} 10{sup {minus}7}{degree}C{sup {minus}1} and 8.3 {times} 10{sup {minus}7}{degree}C{sup {minus}1}, RT = 1,000{degree}C), thermal-induced misfit stresses will be developed. Because of these stresses, toughening effects can be expected in the composite microstructures.
- OSTI ID:
- 6073860
- Journal Information:
- Advanced Ceramic Materials; (USA), Journal Name: Advanced Ceramic Materials; (USA) Vol. 2:4; ISSN 0883-5551; ISSN ACEME
- Country of Publication:
- United States
- Language:
- English
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ALKALI METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
CRYSTAL STRUCTURE
DATA
EXPANSION
EXPERIMENTAL DATA
FABRICATION
GRAIN BOUNDARIES
INFORMATION
LITHIUM COMPOUNDS
LITHIUM SILICATES
MICROSTRUCTURE
NITRIDES
NITROGEN COMPOUNDS
NUMERICAL DATA
OXYGEN COMPOUNDS
PHASE STUDIES
PNICTIDES
SILICATES
SILICON COMPOUNDS
SILICON NITRIDES
SINTERING
THERMAL EXPANSION
VERY HIGH TEMPERATURE