Preparation, Microstrucutre And Dielectric Properties Of BaTiO₃-based Nanotube Arrays

The contents of this thesis are preparation of titania nanotube arrays (TiNTs). synthesis of BaTiO3-based nanotube arrays by hydrothermal method with TiNTs as templates, and systematic investigation of dielectric properties of BaTiO3-based nanotube arrays.A variety of TiNTs were prepared in NaF/glycol solution after the parameters of anodic)xidation were picked out the best. With increasing anodic time, the lengths of nanotubes vere controlled as long as several μm in NaF/glycol solution. In which the morphology of lanotubes are better and the inner diameters of nanotubes range from50nm to100nm.Hydrothermal temperature, the concentration of hydrothermal solution. Indrothermal eaction time and the templates, which affects the morphology of BaTiO3nanotubes. were comprehensively discussed in hydrothermal method with TiNTs as templates prepared in NaF/glycol solution. The results revealed that perovskite BaTiO3nanotubes with a good crystalline could be gained when the reaction temperature reduced to100℃. The ransformation from TiO2to BatiO3showed a positive proportion relationship with the lydrothermal temperature and hydrothermal reaction time, the same phenomena also lappened at the sizes of sidewalls.The structure, composition and ferroelectric properties of BaTiO3nanotuhes were characterized by XRD and SEM. The phase state of as-prepared nanotubes showed cubic bhase whose diffraction strength increased with increasing hydrothermal temperature:It could be controlled outer diameters at the range of80nm to150nm and tube lengths500nm to12μm. After500℃annealing treatment, the mixture structure of tetragonal and cubic phase could be obtained. The shape of tube could not be stabled at the temperature as high as700℃or so. BaxSr1-xTi03nanotubes were successfully prepared via hydrothermal reaction at200℃. and with the increasment of Sr ion, the diffraction plane (110) shifted to the higher diffraction ingle.At last, the dielectric behaviors of BaTiO3, BaxSr1-xTiO3nanotubes and Mg-doped lanocrystalline BaTiO3ceramics were investigated. The results show that, barium titanate ceramic dielectric constant which is detected between a low frequency and sound frequency ises considerably after the magnesium doped, but the appearance of the oxygen vacancy after he magnesium doped, thereby, the dielectric loss of magnesium doped barium titanate ceramics improves; the ferroelectric phase transition changed, cubic phase to tetragonal phase ransition temperature reduced to about350K; hydrothermal reaction time and hydrothermal-eaction temperature rise are beneficial to improving the BaTiO3dielectric properties: ferroelectric barium titanate nanotubes, increasing heat treatment temperature is helpful to mprove the dielectric constant; Sr doped barium titanate nanotubes improved dielectric properties.