中温域固体酸化物燃料電池用の電解質

概要

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Fluorite oxide solid electrolytes with emphasis of doped ceria are reviewed in terms of electrical conductivity, diffusivity and transference number. The electrical conductivity and diffusion constant of various fluorite compounds are compared and those of ceria-based oxides are almost the highest among these fluorite oxides. The electrical conductivity of doped ceria is much dependent of the kind and the concentration of dopants. The reason for this behavior is qualitatively given as due to the defects associate between dopant cations and oxygen vacancies and the comparison between the theory and the experiment is presented. In order to decrease the activation energy in the electrical conductivity of doped ceria, it is suggested that the dopant cation with the critical radius, which is about 0.111 and 0.104 nm for di-valent and tri-valent cations, respectively, is desirable to choose. The effect of sample preparation on the electrical conductivity is described in terms of the character of raw materials, impurities and the sintering condition. The factors to determine the transference number and the methods to increase the transference number at low oxygen pressures are also described.
横浜国立大学の論文