In-situ Raman observation on crack tips of Vickers indent in PLZT ceramics

Vickers indentation was introduced into the originally in-plane and out-of-plane poled PLZT ceramics. The Raman spectra were in-situ recorded at selected crack tips before and after the indentations, as well as after the applications of external electric field. The results show that the changes in Raman intensities of optical modes could be sensitively related to 90 degrees domain switching around the crack tips which are strongly dependent on the directions of original polarization and geometric locations. When the direction of electric field was perpendicular to the direction of original polarization, the 90 degrees domain switching at crack tips of the Vickers indentation on the originally in-plane poled PLZT ceramics caused most significant change in the Raman intensity, which inhibited the crack growth. However, when the direction of electric field was parallel to the direction of original polarization, the growth of crack tips became predominantly without the 90 degrees domain switching, which led to the crack growth.