The microstructure of a pressureless sintered (1605°C, 90 min) O′+β′ SiAlON ceramic with CeO2 doping has been investigated. It is duplex in nature, consisting of very large, slablike elongated O′ grains (20–30 μm long), and a continuous matrix of small rodlike β′ grains (< 1.0 μm in length). Many α‐Si3N4 inclusions (0.1–0.5 μm in size) were found in the large O′ grains. CeO2‐doping and its high doping level as well as the high Al2O3 concentration were thought to be the main reasons for accelerating the reaction between the α‐Si3N4 and the Si‐Al‐O‐N liquid to precipitate O′–SiAlON. This caused the supergrowth of O′ grains. The rapid growth of O′ crystals isolated the remnant α–Si3N4 from the reacting liquid, resulting in a delay in the α→β‐Si3N4 transformation. The large O′ grains and the α‐Si3N4 inclusions have a pronounced effect on the strength degradation of O′+β′ ceramics.
|Original language||English (US)|
|Number of pages||4|
|Journal||Journal of the American Ceramic Society|
|State||Published - Aug 1994|
ASJC Scopus subject areas
- Ceramics and Composites
- Materials Chemistry