Preparation of solid electrolyte nano-sized powders and examination of relationship between oxide tonic conductivity and nano- structural features in sintered bodies

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For a design of high quality doped CeO_2 solid electrolytes, the oxide tonic conductivity must be maximized and the n-type semi-conducting property must be minimized into the specimens. In order to achieve them, we observed the micro-structure at atomic scale. Also we examined the relationship between electrical conductivity and micro-structural features in the doped CeO_2 sintered bodies. In the present study, we prepared the 20 kinds of specimens which are the electrolytes (Sm_xCe_<1-x>O_<2-x/2> and Gd_xCe_<1-x>O_<2-x/2>, x=0.05, 0.1, 0.15, 0.2 and 0.25) and n-type semi-conductors (Ho_xCe_<1-x>O_<2-x/2> and Tb_xCe_<1-x>O_<2-x/2>, x=0.05, 0.1, 0.15, 0.2 and 0.25) to examine the relationship between physical properties (i.e. electrical conductivity, activation energy, and so on) of sintered bodies and nano-structural features in sintered bodies. The average particle size of powders prepared by carbonate co-precipitation method was approximately sonm. The aforementioned specimens were d … More ensified more than 95 % of theoretical density. The conductivity in the sintered bodies was measured using direct current measurement method. The observation of micro-structural features at atomic scale was performed using transmission electron microscopy (TEM). The micro-domains with ordered structure of oxygen vacancy were observed in the electrolytes (i.e. Sm_xCeCe_<1-x>O_<2-x/2> and Gd_xCe_<1-x>O_<2-x/2>. The conductivity in those sintered bodies was decreased with increasing micro-domain content and micro-domain size. On the other hand, the small precipitates were observed in Ho_xCe_<1-x>O_<2-x/2> and Tb_xCe_<1-x>O_<2-x/2> sintered bodies. The huge amount of Ce^<3+> and do pant cation was observed into the precipitates. In the case of Ho_xCe_<1-x>O_<2-x/2> and Tb_xCe_<1-x>O_<2-x/2> sintered bodies, the typical n-type semi-conducting property was observed. Accordingly, for a design of high quality doped CeO_2 solid electrolytes, it is concluded that the micro-domain size must be minimized in the doped CeO_2 sintered bodies and the precipitates must be removed from the doped CeO_2 sintered bodies. Less