| Summary: | 碩士 === 國立臺北科技大學 === 製造科技研究所 === 98 === The goal of this research is for the dielectric constant of sintered barium titanate to be increased by external DC electric field. There is other way could also reach this goal by element doping, but the crystalline phases become really complicated for further analyses and thus the costs of materials and manufacturing rise due to the additional elements added. So, it’s simpler through high voltage polarization to increase dielectric constant.
Various Ba/Ti ratio powders are manufactured by solid-state method and which are all pressed into round pellets then sintered at different temperature by high temperature furnace. After sintering, SEM is introduced for morphology observation of bulk specimens with various Ba/Ti ratios at different sintered temperature. At the meantime, Raman is used for bulk specimens to observe the differences in specific peaks between Ba/Ti ratios individually, then dielectric constant before and after polarization are calculated by capacitance. Thus the parameters which possess the best dielectric constant can be found.
Through literatures and experiments, we found that the micro-structure will influence the dielectric constant indeed. Specimens with better density and larger grain size could drop the dielectric constant, while specimens with lower density and smaller grain size could increase the dielectric constant. These are affected by micro-structure, and which will influence polarization as well. After polarization, we found the level of ratio 1.002 increases the most, ratio 1.01 and 1.05 followed, then the worst of all is the ratio smaller than one. Furthermore, smaller grain size possess lower dielectric constant due to surface effect, while larger grain size will drop dielectric constant. Thus we assume that the best sintering temperature is at 1280℃ and 1290℃.
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