Raman spectroscopic evidence of a coherent room temperature hybrid structure of BaTiO3 single crystal

Abstract

Recently, a precession X-ray study has discovered that ferroelectric BaTiO3 single crystals have a, coherent hybrid structure that consists of tetragonal and monoclinic lattices that share the (101) face of the tetragonal [11, 12]. Microscopic observations attest that the single crystal has two kinds of stripes (dark and white regions). Raman spectra of all sides of the cubic crystal have been collected at several scattering configurations. Two kinds of domains have been observed by the Raman measurements within the stripes, which are identified as light and dark spots under the optical microscope. The spectra structures and line widths are strongly affected when the laser direction is parallel to the 6-axes and the polarization parallel to the a- or c-axes of the 90° domain (ac-side). It appears that there is a symmetry reduction and disorder, which affects the Raman active phonons. The results are in agreement with the coexistence of the two (tetragonal and monoclinic) lattices.