Investigation On The Synthesis And Properties Of One-dimensional Na_0.5Bi_0.5TiO₃nanomaterial

Sodium bismuth titanate (Na0.5Bi0.5TiO3, NBT), is a perovskite ferroelectric compound with A-sit ions replaced.It is well known that NBT possesses high remanent polarization, large remnant polarization, high piezoelectric constant and, low dielectric constant and other characters at room temperature, which is of interest as a new candidate lead-free ferroelectric material. On other hand, One-dimensional ferroelectric nanomaterials have attracted much attention in recent years because of their unique properties from bulk-structures which derived from quantum size effect in nanodevices. Therefore synthesis and properties of one-dimensional NBT nanomaterial have important significance as well as potential applications in nanodevices. In this thesis, three methods were used to prepared NBT one-dimensional nanomaterial, include nanobelts, nanorods and nanotubes, and the optical and electrical properties have been studied. The main results were as follows:(1) NBT nanobelts were successfully prepared by the hydrothermal method with Bi(NO3)3·5H2O, TiO2and NaOH as the starting materials. Hydrothermal synthesis conditions were studied by XRD and SEM, when the synthesis temperature is220℃,10M NaOH concentration, single-crystalline NBT nanobelts with diameters up to micrometer were synthesized. Moreover, the FTIR, Raman,UV-Vis and PL properties were also investigated. The FTIR and Raman are obvious blue-shift than NBT nanoparticles. And Raman spectrum shows that the vibration modes of NBT nanobelts which certified the perovskite structure. The band gap energy of NBT nanorods is about3.35eV. When the excitation wavelength is270nm, three emission peak were founded.(2) NBT nanorods were successfully prepared by the sol-gel hydrothermal method with NaOH as a mineralizer. Alkaline concentration had a great effect on the crystallization and morphology of the resultant powders. In hydrothermal condition of200°C and10M NaOH concentration, single-crystalline NBT nanorods with diameters of about100nm and length of reaching up to5μm were synthesized, and the growth is generally along the [010] direction. Moreover, the FTIR, UV-vis, Raman and photocatalytic property of the as-obtained NBT micro/nanostructures were also investigated. FTIR spectrum broadened comparing to that of macro-particle, and Raman spectrum shows that the vibration modes of NBT nanorods. The band gap energy of NBT nanorods is about3.38eV. Photocatalytic properties of the nanorods were Obviously superior to particles by the photo-decolorization of MB aqueous solution.(3) NBT nanotube arrays were synthesized by sol-gel processing with anodic aluminum oxide templates.The annealing temperature and environment were studied, the most appropriate conditions are the temperature is700℃and in Oxygen. The as-prepared samples are monoclinic phase perovskite structure with the outer-diameter of about200nm and wall thickness of about20nm, corresponding to the pores diameters of the AAO templates employed. Polarization-electricfield (P-E) response curves of NBT nanotube arrays were measured, which showed that the remanent polarization (Pr) and the coercive electric field (Ec) are about1.15μC·cm-2and158kV·cm-1, respectively.