Study On Synthesis Of BaTiO₃ , SrTiO₃ And Ba_1-xSr xTiO₃ Nanomaterials

BaTiO₃, SrTiO₃ and Ba_1-xSr_xTiO₃ are important electronic ceramic materials, possess excellent properties of ferroelectricity, piezoelectricity, with stand voltage and insualting and have extensive application in various fields. Many scientists have paid great attention to the nanomaterials due to their excellent physical chemistry properties and the prospect of its application. With the development of the nanotechnology, many synthesis methods have been adopted to prepare nanomaterials. Among these methods, the hydrothermal method, low-temperature calcination and molten salt method have aroused the scientist's attention, and the reason is that they can effectively control the particle morphology and size of the products. BaTiO₃, SrTiO₃ and Ba_1-xSr_xTiO₃ nanoparticles have been synthesized through these methods and the factors that have effect on the morphology and particle size have also been studied.Ba0.7Sr0.3TiO₃ nanoparticles was successfully prepared by the hydrothermal method, using TiO₂ nanotube as precursors, which had been prepared by the hydrothermal method in advance, and using Ba(Ac)₂, Sr(Ac)₂·H₂O as starting materials (the other barium strontium titanate with different composition can be prepared by the same method by changing the amount of substance ratio of barium and strotium). The effects of the alkali concentration on the products particle size and morphology were studied. The as-synthesized products were characterized by XRD, SEM, TEM, HRTEM, UV-Vis, PL and FT-IR. The results show that the product is single crystal with particle sizes of 25–50 nm and cubic phase structure, and the particle size of the products become smaller with increasing of the alkali concentration, but higher alkali concentration will lead to the increasing in particle diameter of the products. UV-Vis analysis exhibits that the bandwidth of Ba0.7Sr0.3TiO₃ is Eg=3.31 eV. In addition, the effect of photocatalytic degradation methlene blue was also investigated. The results show that the degradation rate of methylene blue is up to 43% after 120 min degradation by adding 0.5 g catalyst into 200 mL methylene blue solution with concentration of 10 mg/L under ultraviolet light.SrTiO₃ nanoparticles were successfully prepared by solid phase grinding-low temperature (400–600℃) calcination method, using strontium hydroxide and tetrabutyl titanate as starting materials. It is confirmed that the strontium titanate nanoparticles with uniform size distribution and particle sizes of 10–40 nm, similar to spherical shape, are cubic perovskite structure. The crystal lattice spacing d and the constantαbecome smaller and the particle size become larger as the increasing of calcination temperature. The precursor, BaO₂·H₂O₂ , was prepared from the reaction of BaCl2·2H2O and H₂O₂ in NH₃·H₂O aqueous solution under the ambient condition. BaTiO₃ nanoparticles were produced by molten salt method using H₂TiO₃ and the as-prepared precursor BaO₂·H₂O₂ as reactants, KNO3 and KOH as a flux. XRD, SEM, TEM, EDS and FT-IR techniques were used to characterize the structures, morphologies and compositions of the products. The results show that BaTiO₃ nanoparticles with uniform size distribution and particle sizes of 25–50 nm, similar to spherical shape, can be obtained through calcining an mixture of the molten salt at 500–600℃for 24 h, and the structures of the as-obtained nanoparticles are of cubic phases. As the increases of reaction temperature, the cell parameters of BaTiO3 nanoparticles decrease, and the crystallite sizes increase. In addition, the formation mechanism of BaTiO3 nanoparticles prepared by molten salt method was also discussed.