抄録
The domain switching near the fatigue crack tip was observed by synchrotron X-ray diffraction and AFM for non-poled and poled PZT specimens. The diffraction patterns taken from a local area of 100μm in diameter were processed to obtain the ratio, I_<004>/I_<400> , of the integrated intensity of 400 to 004 diffractions as a measure of domain switching. The intensity ratio, I_<004>/I_<400> was decreased both at the notch root and the tip of fatigue cracks, suggesting the 004 direction aligned on the specimen surface and perpendicular the crack line due to fatigue loading. The amount of domain switching near the crack tip is larger for NP specimen than for PL specimen, which corresponds to the larger resistance of NP specimens to crack growth. The domain switching near the crack tip occurring under load was detected as the depression zone by AFM. The size of the depression zone observed at the maximum load was about 6μm which was equal to the grain size, and the zone disappeared when unloaded. The depth of the depression zone changes as a function of the applied load, and the relation between the depth and the applied load showed a hysteresis loop. The amount of loop expansion of hysteresis was larger in NP specimen, and the load at the onset of depression was also larger.
