Synthesis And Characterization Of Submicron Titanate Crystallites

The present thesis is focused on exploring mild and simple methods to synthesize some important titanate materials via designing novel systems and processes. It is aimed at minishing pollutions and energy waste, reducing the costs, as well as controlling the purity and size of the resultant products. Furthermore, many modern analysis techniques including powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scan electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (Raman), electrochemical workstation, etc., were used to characterize the as-synthesized products, and the possible formation mechanisms of the titanate products were also proposed. The main works completed are summed up as following:1. Submicrometer-sized BaTiO₃ crystallites in tetragonal structure were synthesized by a novel low temperature liquid-solid reaction method, which mainly involved two simple steps: firstly, BaO₂·H₂O₂ submicron particles (about 130- 450 nm) were precipitated from the reaction of BaCl₂ and H₂O₂ in an alkalescent (pH = 8) aqueous solution under the ambient condition; secondly, tetragonal phase BaTiO₃ submicrocrystals with the size in the range of 180 to 400 nm could be produced by subjecting the as-prepared BaO₂·H₂O₂ (excess) and commercial TiO₂ submicron particles to thermal treatment in air at 700°C for 10 h, combined with a subsequent washing process using 1 mol/L HNO₃ aqueous solution and distilled water. The structure, composition and electrical properties of the obtained products were characterized by XRD, Raman, FTIR, XPS, ICP-AES, SEM, and electrochemical workstation, etc. The possible formation mechanism of BaTiO₃ in this system was also proposed.2. High purity CdTiO₃ submicrocrystals were synthesized by a low temperature solid phase reaction method, which mainly involved two simple steps: firstly, CdO₂ nanoparticles with the size of about 5 nm were precipitated from the reaction of 3CdSO4·8H₂O and H₂O₂ in an alkalescent aqueous solution (pH = 8.0) under the ambient condition; secondly, ilmenite phase CdTiO₃ crystallites with the size in the range of 150 to 350 nm could be produced by subjecting the as-prepared CdO₂ nanoparticles (excess) and commercial TiO₂ submicron particles to thermal treatment in air at 600°C for 6 h, combined with a subsequent washing process using 1 mol/L HNO₃ aqueous solution and distilled water. The structure, composition and electrical properties of the obtained products were characterized by XRD, Raman, FTIR, XPS, ICP-AES, SEM, and electrochemical workstation, etc. The possible formation mechanism of CdTiO₃ in this system was also discussed.3. The low temperature solid phase and molten salt synthesis of high purity SrTiO₃ submicrocrystals have been achieved mainly via two simple steps: firstly, SrO₂ nanoparticles (about 53 nm) were precipitated from the reaction of Sr(NO₃)₂ and H₂O₂ in an alkalescent aqueous solution (pH = 8.0) under the ambient condition; secondly, cubic phase SrTiO₃ crystallites with the size in the range of 100 to 350 nm could be produced by subjecting the as-prepared SrO₂ nanoparticles (excess) and commercial TiO₂ powders to thermal treatment in air at 700 oC for 10 h (as for molten salt synthesis, in this procedure, appropriate amounts of KCl and NaCl mixture were added to the source materials), combined with a subsequent washing process using 1 mol/L HNO₃ aqueous solution and distilled water. The structure, composition and electrical properties of the products derived from both the solid phase and molten salt methods were characterized by XRD, Raman, FTIR, XPS, SEM, and electrochemical workstation, etc. The possible formation mechanisms of SrTiO₃ in the two systems were also proposed.