The studies of dielectric characteristics for(1-x)Na0.5K0.5NbO3−xCaTiO3lead-free dielectric material system

• Main Author: 林俊德
• Other Authors: 洪群雄 教授
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/17618284388927390836

碩士 === 國立高雄師範大學 === 電子工程學系 === 101 === Because of environmental issue, Lead-based ceramic materials had been inhibited on commercial applications by the International Environmental Organizations. Furthermore, the developments of Lead-free ceramic materials are also great urgency until now. In this work, the suitable application ferroelectric relaxors were investigated for (1-x)Na0.5K0.5NbO3−xCaTiO3 ceramic system. Moreover, we hoped that the Lead-free ceramic materials could be synthesized in the future for suitable manufacturing multi-layers ceramic capacitors. In this thesis, the effects of CaTiO3 dopants, sintering temperature and geometric structure were investigated for (1-x)Na0.5K0.5NbO3−xCaTiO3 ceramic system. Firstly, the phase transition temperature could be decreased, the pyrochlore phase could be suppressed, the composition fluctuation could be enhanced and the disorder state of cations could be increased by adding CaTiO3 compositions for (1-x)Na0.5K0.5NbO3−xCaTiO3 ceramic system. Therefore, the normal ferroelectric properties of Na0.5K0.5NbO3 ceramic system could be modified to the ferroelectric relaxation properties of (1-x)Na0.5K0.5NbO3−xCaTiO3 ceramic system. Secondly, the dielectric behaviors of 0.82(Na0.5K0.5)NbO3−0.18CaTiO3 ceramic system could be controlled by adjusting sintering temperature. When sintering temperature is too low, the pyrochlore phases were induced and the disorder states of cations were enhanced. Therefore, the dielectric dispersions were enhanced by decreasing sintering temperature for 0.82(Na0.5K0.5)NbO3−0.18CaTiO3 ceramic system. The response mechanism of increasing sintering temperature could enhance the order state of cations and modified the dielectric properties from the ferroelectric relaxors to the normal ferroelectric materials for 0.82(Na0.5K0.5)NbO3−0.18CaTiO3 ceramic system. The order states were enhanced with various arrangement types of cations, the random-site type was first enhanced and then the space-charge type was enhanced by increasing sintering temperature. Lastly, the two-layer structure capacitors with different dielectric mediums were fabricated and could realize the temperature-compensation capacitors. In the temperature-compensation range, the dielectric constant almost could not be changed when the environmental temperature was changed. Moreover, the loss tangent could be controlled to be smaller than 0.06 in the temperature-compensation range.