Design of Functional Double Oxides by Solution Processing

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In order to develop highly functional ceramics materials for electronics, ionics, optronics, superconductors, sensors, catalysts, etc., we are required to design and optimize (1) chemical compositions, (2) crystal structures, (3) microstructures, (4) electronic stuructures, (5) dispensions, etc., of double oxides like perovskite-type, spinel-type, and α-NaFeO_2 type, etc. Their properties are also depending upon their synthetic/fabrication processings, thus design and control of the processings are also important. In the present study, we have investigated particularly "Solution Processings" because they give lower environmental impacts than other processings based upon solid state reactions, gas/vapor reactions, especially in vacuum (plasma, ion beam, molecular beam, .....), moreover they have a merit to have the possibility to produce metastable and/or low temperature phases which are difficult to form by using high temperature and/or high energetic processings.We have succeeded in following items ;(1) LiCoO_2 films could be fabricated at as low temperature as -100℃ on various metal substrates in a LiOH solution.(2) It was electrochemically active high-temperature LiCoO_2 phase.(3) A flow-type hydrothermal/electrochemical apparatus has been developed for layered films like BaTiO_3/SrTiO_3/Ti.(4) Water soluble complexes of Ti, Nb, and Ta have been synthesized, which enabled to prepare homogeneous double oxide powders containing these metals.(5) Some new layered double oxides have been developed to exhibit high performances as photo-catalysts.(6) Intercalation of ions, salts, molecules, and/or bio-molecules into layered double oxides can produce new functional nano-hybrids.(7) Materials design for new double oxides has been established to create quantum-ferroelectric materials, high Li-ion conductors, superconductors, etc.These results will open a new horizon of materials sciences and technologies.