| Summary: | 碩士 === 國立高雄應用科技大學 === 化學工程系碩士班 === 92 === Nanometeric-sized BaTiO3 powders were synthesized from titanium acetylacetone precursor, which was obtained by chelating acetylacetone with titanium isopropoxide, reacted with barium ion in a strong alkaline solution (pH>13). The effects of such preparatory conditions on the molar ratio of acetylacetone/titanium alkoxide, the molar ratio of water/titanium alkoxide, pH-value, the reaction temperature and stirring speed were systematically studied using 3-level orthogonal array design.
At a higher stirring speed of 750 rpm, nanometric-sized BaTiO3 powders of 80 nm were obtained. On the contrary, a relative larger particle size of about 350 nm was prepared at a lower stirring speed at 250 rpm. At higher temperature such as 100℃, the synthesized powder exhibited a high crystallinity of perovskite phase, but those prepared at 40-50℃ will produce impurities of barium carbonate. By applying a 3-level orthogonal array, L27(313), and calculated by Minitab software, the optimal conditions were prepared by using 5M KOH(aq), stirring speed 465 rpm and reaction temperature 100℃. Molar ratios of 10 and 4 were prepared for H2O/Ti(O-iC3H7)4 and acetylacetone/Ti(O-iC3H7)4, respectively.
Besides, various HLB values of PANNOX series surfactants were also applied to improve the quality of BaTiO3 powders. It was found that the higher HLB value of surfactant was used, a finer BaTiO3 powder was synthesized. However, as the increase of HLB value of surfactant was applied, the decrease of DSEM/DBET in powder was obtained. A higher value of dielectric constant was obtained by preparing the BaTiO3 powder in good dispersity, which will result a readily sintered property of bulk.
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