a b s t r a c tAlkali metal (Li + , Na + , K + ) intercalated titanate nanotubes have been studied by vibrational spectroscopy (Raman and FT-infrared), X-ray diffraction, and electron microscopy. The vibrational spectroscopic data shown that the most affected vibrational mode is that related to Ti-O bond whose oxygen is not shared among the TiO 6 units of the framework structure. A correlation between vibrational frequency shifts and intercalated metal was found, thus showing that vibrational spectroscopy is very useful for probing metal intercalated titanate nanotubes. Our results provide good evidences that the structure of titanate layers in titanate nanotube, a subject of long debate in the literature, is similar to trititanates (like Na 2 Ti 3 O 7 ).
Bi 4−x La x Ti 3 O 12 materials were synthesized by the sol-gel process and thin films were prepared on Pt (i.e., Pt/TiO2/SiO2/Si) substrate by spin coating. Structural properties of the films were examined by x-ray diffraction and Raman spectroscopy. Dielectric and ferroelectric response was studied for 0.63-μm-thick Bi3.44La0.56Ti3O12 films. Butterfly dielectric behavior and remnant polarization of up to Pr=41 μC/cm2 has been achieved. These films also showed fatigue free response up to 109 switching cycles. On the basis of these studies, large polarization in Bi3.44La0.56Ti3O12 films is attributed to dipole formation which may tilt TiO6 octahedra to Bi2O2 interlayer.
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