Tetragonal Barium titanate (BaTiO3) nanotube arrays have been prepared using the template-assisted hydrothermal method combined with an annealing process. The in-situ chemical conversion of TiO2 nanotube array templates ensured that BaTiO3 maintained the morphology of the nanotube architectures. Moreover, X-ray diffraction and Raman spectrum characterization were used to confirm that the BaTiO3 nanotube arrays had a tetragonal phase after the use of a simple annealing technique. Typical hysteresis loops showed their ferroelectricity, with the remanent polarization and coercive fields being 2.57 microC/cm2 and 2.52 kV/cm, respectively. The relative dielectric constant of the tetragonal BaTiO3 nanotube arrays reached up to 1000 and the dielectric loss was as low as 0.02 at 1 kHz at room temperature.

1Living diatoms show a promise for applications in various fields in particular for the fabrication of micro/nano devices. This study acquired pure diatom walls (frustules) by several steps including collection, separation, and pure culture of marine diatoms. A two-step acid cleaning and baking method was adopted to purify biosilica structures from the diatoms. Results indicated that the morphology of the diatom frustules began to change at a baking temperature of 700 °C. With rising temperatures, the damage to the diatom frustules was more severe, but the composition was less affected by temperature. Therefore, an optimal parameter of 600 °C, 1 °C min, and 2 h was set for our study. However, because of the species-specific differences, the morphology and composition of the different frustules were not identical at the optimal parameter.