Design of Functional Double Oxides by Solution Processing

为了开发用于电子学、离子学、光电子学、超导体、传感器、催化剂等的高功能陶瓷材料，我们需要设计和优化（1）化学成分，（2）晶体结构，（3）微观结构，（4）电子结构，（5）配方等，钙钛矿型、尖晶石型和α-NaFeO_2型等复合氧化物的性能也取决于其合成/制备工艺，因此工艺的设计和控制也很重要。在本研究中，我们特别研究了“溶液处理”，因为它们比基于固态反应、气体/蒸气反应的其他处理，特别是在真空中（等离子体、离子束、分子束等），我们在以下几个方面取得了成功：（1）在LiOH溶液中，可以在-100℃的低温下在各种金属衬底上制备LiCoO_2薄膜。(2)它是电化学活性高温LiCoO_2相。(3)研制了一种用于BaTiO_3/SrTiO_3/Ti等层状薄膜的流动式水热/电化学装置。(4)合成了Ti、Nb和Ta的水溶性络合物，从而能够制备含有这些金属的均匀双氧化物粉末。(5)近年来，一些新型层状复合氧化物材料被开发出来，表现出良好的光催化性能。(6)将离子、盐、分子和/或生物分子嵌入层状双氧化物中可以产生新的功能性纳米杂化物。(7)新的双氧化物材料设计已建立起来，用于制造量子铁电材料、高锂离子导体、超导体等，这些结果将开辟材料科学和技术的新视野。

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.