Some new aspects of microstructural design of Beta-Si3N4 ceramics

A possibility in tailoring microstructures and properties of silicon nitride ceramics is demonstrated by the use of fine .beta.-Si3N4 powders. Fine powders were produced by plasma-chem. synthesis and by crystn. of amorphous Si3N4 in the presence of an oxide nitride liq. A wide range of microstructures can be obtained depending on sintering and powder characteristics. At low sintering temps., microstructures consisting of nanosized, equiaxed grains were obtained, whereas at high temps. or long sintering times microstructures consisting of fine needle like grains were formed. Microstructural anal. revealed a high anisotropic grain growth of .beta.-grains in the fine grained ceramic.