Hot-pressed silicon nitride with various lanthanide oxides as sintering additives
The effects of addition of various lanthanide oxides and their mixture with Y2O3 on the sintering of Si3N4 were investigated. The addition of simple and mixed lanthanide oxides promoted the densification of Si3N4 in hot-pressing at 1800 C under 300-400kg/ centimeters squared for 60 min. The crystallization of yttrium and lanthanide-silicon oxynitrides which was observed inn the sintered body containing yttrium-lanthanide mixed oxides as additives led to the formation of a highly refractory Si3N4 ceramic having a bending strength of 82 and 84 kg/millimeters squared at room temperature and 1300 C respectively. In a Y2O3+La2O3 system, a higher molar ratio of La2O3 to Y2O3 gave a higher hardness and strength at high temperatures. It was found that 90 min was an optimum sintering time for the highest strength.
- Research Organization:
- National Aeronautics and Space Administration, Washington, DC (USA)
- OSTI ID:
- 6176405
- Report Number(s):
- N-84-28916; NASA-TM-77424
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SILICON NITRIDES
SINTERING
ADDITIVES
CERAMICS
HARDNESS
HOT PRESSING
LANTHANUM OXIDES
YTTRIUM
CHALCOGENIDES
ELEMENTS
FABRICATION
LANTHANUM COMPOUNDS
MATERIALS WORKING
MECHANICAL PROPERTIES
METALS
NITRIDES
NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PNICTIDES
PRESSING
RARE EARTH COMPOUNDS
SILICON COMPOUNDS
TRANSITION ELEMENTS
360201* - Ceramics
Cermets
& Refractories- Preparation & Fabrication