摘要 : Electrochemical properties of Mg~-, Fe~- or Co~-substituted K_2NiF_4-type Sr_2TiO_4-based oxide solid solutions were investigated and compared to those of indium substituted system, which had been confirmed to be a protonic conduc... 展开 Electrochemical properties of Mg~-, Fe~- or Co~-substituted K_2NiF_4-type Sr_2TiO_4-based oxide solid solutions were investigated and compared to those of indium substituted system, which had been confirmed to be a protonic conductor. All samples were prepared using the conventional solid-state reaction method. The solubility limit of Mg for Sr_2TiO_4 was about 0.05, just the half of solubility limit of In, 0.1. The dependence of electrical conductivities of Sr_2Ti_(1-x)Mg_xO_(4-δ) on x was very similar to that of conductivities of Sr_2Ti_(1-x)In_xO_(4-δ) on x/2. EMF's of hydrogen or oxygen concentration cells using Sr_2Ti_(0.97)Mg_(0.03)O_(4-δ)< /sub> as a solid electrolyte were the same as those using Sr_2Ti_(0.93)In_(0.07)O_(4-δ)< /sub>. These results indicate that in the Sr_2TiO_4-based system the predominant factor governing the phase relation and protonic conduction properties is the concentration of introduced oxygen vacancies. Single phase samples of Fe- or Co-substituted solutions, Sr_2Ti_(0.93)Fe_(0.07)O_(4-δ)< /sub> and Sr_2Ti_(0.93)Co_(0.07)O_(4-δ)< /sub> were obtained. In Sr_2Ti_(0.93)Fe_(0.07)O_(4-δ)< /sub>, the dependence of conductivity on oxygen partial pressure was qualitatively equal to that of Sr_2Ti_(0.93)In_(0.07)O_(4-δ)< /sub> indicating that the valence state of Fe is settled at +3 (3d5) in Sr_2Ti_(0.93)Fe_(0.07)O_(4-δ)< /sub> and five d-electrons of Fe~(3+) are localized. In Sr_2Ti_(0.93)Co_(0.07)O_(4-δ)< /sup>, the dependence of conductivity on oxygen partial pressure was different from those of Sr_2Ti_(1-x)M_xO_(4-δ) (M = In, Mg and Fe). There were neither pure ionic conduction regions at intermediate PO(2) nor n-type electronic contributions to conductivity in low PO(2) in Sr_2Ti_(0.93)Co_(0.07)O_(4-δ)< /sub>. 收起