Study of Correlation between Ionic Transport and the Structure of Solids

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The structure of solids is one of primary factors to determine their ionic transport property. The purpose of the present study is to search the guiding principles for the development of solid matters with extraordinarily fast ionic transport through a systematic understanding about the correlation between the structure and transport properties. We selected the following three typical structures or compounds suitable for this research purpose ; (1) layered oxides, (2) the LISICON and perovskite framework structures (3) aggregates of metal oxide clusters, and (4) composite glass phases. Principal results obtained with each item are summarized as follows. (1) Chemical diffusion measurements for layered LiィイD21-xィエD2NiィイD21+xィエD2OィイD22ィエD2 showed that lithium diffusion is enhanced with decreasing nonstoichiometry (x) of the compound. (2) New LISICON type compounds in the systems LiィイD22ィエD2S-GeSィイD22ィエD2-ZnS and LiィイD22ィエD2S-GeSィイD22ィエD2-GaィイD22ィエD2SィイD23ィエD2 (thio-LISICON) have been synt … More hesized, which show very high lithium conductivity at room temperature (10ィイD1-4ィエD1ScmィイD1-1ィエD1). XAFS measurements of perovskite type proton conductors, Sr(ZrィイD20.9ィエD2YbィイD20.1ィエD2)OィイD23ィエD2 and Sr(CeィイD20.9ィエD2YbィイD20.1ィエD2)OィイD23ィエD2, revealed that the the interatomic distances (Zr-O and Yb-O) are changed by introduction of hydrogen into the compound. (3) Proton conductors based on tungsten oxide cluster aggregates with acidic functional groups have been obtained from a solution mixture of peroxo-polytungstate and oxalic acid (or malonic acid). Conductivity is increased with increasing with the ligand content and reaches 10ィイD1-3ィエD1ScmィイD1-1ィエD1 (25℃) at Ox/W=0.4. (4) The hierarchic dynamics of conductive ions in glass phases like CuI-CuィイD22ィエD2MoOィイD24ィエD2 has been revealed by various measurement techniques including the neutron scattering and the X-ray small angle scattering. Conductivity of organic-inorganic mixed glasses containing LiィイD1+ィエD1 such as LiI-(CィイD22ィエD2HィイD25ィエD2)ィイD24ィエD2NI has also been investigated. Less