P. Sajgalik et al., RELATIONSHIP BETWEEN MICROSTRUCTURE, TOUGHENING MECHANISMS, AND FRACTURE-TOUGHNESS OF REINFORCED SILICON-NITRIDE CERAMICS, Journal of the American Ceramic Society, 78(10), 1995, pp. 2619-2624
Different microstructures in Si3N4 ceramics containing Y2O3 and Al2O3
as sintering additives were prepared by two-step sintering, Pull-out a
nd elastic bridging were most frequently observed as the toughening me
chanisms in samples with fine-grained microstructures having needlelik
e beta-Si3N4 grains with diameters of <1 mu m. Crack deflection was th
e main toughening mechanism observed in samples with coarse-grained mi
crostructures having grains with diameters of >1 mu m. The values of f
racture toughness mere varied from 6.1 to 8.2 MPa . m(1/2) with respec
t to the microstructural characteristics, characterized by the volume
fraction of needlelike grains and their diameter.