Hugoniot-compression curves for Si
3N
4 ceramics with controlled microstructure were measured to study the yielding properties under shock compression, and the correlation with the microstructural characterization and the static mechanical strength. Hugoniot-measurement experiments were performed on 4 kinds of Si
3N
4 ceramics by means of the inclined-mirror method combined with a powder gun. The Hugoniot-elastic limits of fine-grained Si
3N
4 ceramics and the SiC whisker-reinforced Si
3N
4 ceramics (within 14-20GPa) were greater than the conventional Si
3N
4 (10-12.5GPa). It was found that the strength of Si
3N
4 ceramics under shock compression is strongly influenced by their microstructure, and the key to the high Hugoniot-elastic limit is to achieve a fine-grained microstructure or a composite structure containing high-strength materials such as SiC whiskers. It was also pointed out that the yield strength per unit weight under shock compression of the Si
3N
4 monolithic ceramics was proportinal to the static strength, but the yield strength per unit weight under shock compression of the SiC whisker reinforced Si
3N
4 was comparatively larger than that of monolithic Si
3N
4. In addition, it was suggested that the Hugoniot-measurement experiments are useful for evaluating the performance of ceramics, because the ceramics show the strength close to the intrinsic value under shock compression, due to the very high strain rate at the shock wave front.
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