Observation of Domain Structures in Tetragonal Pb(Zr_xTi_1-x)O₃ Single Crystals by Chemical Etching Method

Domain structures in tetragonal Pb(Zr_xTi_1-x)O₃ (PZT) single crystals etched by HF+HCl solution were observed by means of a scanning electron microscope. The relationship between the etch patterns of pseudocubic {100} faces and spontaneous polarization vectors was examined using micro-Raman spectroscopy and electron channeling patterns. Both the a-face and the positive c-face are quickly etched, but the former results in a rough surface while the latter results in a smooth one. The negative c-face is rather slowly etched. Another type of etch pattern with a wedge-shaped section was observed; this is usually observed in PZT ceramics but has not been reported in BaTiO₃. This pattern can be explained by the difference in etch rates between various {100} faces and the peculiar domain structures which consist of a single domain region with narrow or wedge-shaped 90° domains. It is assumed that such a domain structure is, although unstable under electrical stress, stable under mechanical stress.