We constructed a scanning near-field optical microscope (SNOM) on a commercially available atomic force microscopy (AFM) apparatus
(SPM-9500J2; Shimadzu Corp.) to measure the stress distribution in ceramic composite materials. Features of our SNOM system
are: (1) a compact SNOM head substituted for the original AFM head; (2) a wide scanning range (125 × 125 μm
2) inherited from the original scanner; (3) use of conventional shear-force regulation; (4) an optical system for the illumination-collection
(I-C) mode; (5) excitation by a 488 nm line of an Ar-ion laser, and (6) light detection by photon counting or a polychromator
equipped with an electronically cooled charge coupled device (CCD). This SNOM system was used to measure the surface structure
and stress distribution of an Al
2O
3/ZrO
2 eutectic composite. We simultaneously measured topographic images and fluorescence spectra of an Al
2O
3/ZrO
2 eutectic composite. We estimated its peak intensity, peak position, and peak width from the fluorescence spectrum during
scanning, which respectively correspond to the abundance of Al
2O
3, stress in the grain, and the anisotropy of that stress. Mapping images showed that the stress and its anisotropy were weaker
in the center of the Al
2O
3 grain than its boundary between Al
2O
3 and ZrO
2. That observation suggests that Al
2O
3 underwent intense anisotropic stress induced by volume expansion in the phase transition of ZrO
2 from the cubic phase to the monoclinic phase during preparation.
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