Low-Temperature, Solution-Based Chemical Synthesis And Property Of Several Perovskite Ferroelectronic Materials

Barium strontium titanate (BST) functional ceramic materials have been widely studied in many fields because of their novel electric and optic properties. Based on the recent advances on solution methodologies to synthesize nanomaterials, we have explored a general method to synthesize a series of barium strontium titanate (BaxSr1-xTiO3, BST) nanocrystals at the room temperature. We also discussed the growth process and mechanism of SrTiO3 nanocrystals, which has a hierachical structure. This synthesis route is simple and mild, and reactants are easy to obtain. The products are well crystalline with pure phase and uniform sizes. The main results could be summarized as follows:1. Simply mixing the SrCl2·6H2O/alkali water solution and titanium isopropylate ethanol solution, without any surfactant or additives at room temperature, will result in the formation of crystalline SrTiO3. The influences of some parameters such as pH value, the volume ratio between water and ethanol and the reaction time have been investigated. The results showed that the pH value played an important role in the formation of hierachical structures. The time dependent study shows that the growth of nanocrystals obeyed the Oswald ripening process.2. A series of barium strontium titanate (BaxSr1-xTiO3, BST) nanocrystals can be produced by using the above route. The ICP-AES analysis shows that the stoichiometric concerntration of Ba/Sr corresponding to the starting mole ratio exactly. XRD spectra revealed the shifting of the 2θ value for (200) diffraction peak. The dielectric constant of BST was measured by sintering and annealing process. Compared with the commercial BST, as-prepared sample has a much higher dielectric constant.3. As-prepared BST nanocrystals were used as photocatalyst to deoxidize HAuCl4 and the Au@BST composite can be prepared. The size of Au nanoparticle is about 15 nm. The quality of Au nanoparticles are much better if the (100) surfaces of BST crystals exposed fully. We also found that even under the usual lighting conditions, BST nanoparticles could deoxidize the HAuCl4 slowly.