Design of Functional Double Oxides by Solution Processing

为了开发用于电子、离子、光电子、超导体、传感器、催化剂等领域的高性能陶瓷材料，我们需要对钙钛矿型、尖晶石型、α-NaFeO_2型等双氧化物进行设计和优化(1)化学成分、(2)晶体结构、(3)微结构、(4)电子结构、(5)配剂等方面的研究。它们的性能也取决于它们的合成/制造工艺，因此工艺的设计和控制也很重要。在目前的研究中，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对环境的影响更小，特别是在真空中（等离子体，离子束，分子束，.....），而且它们有可能产生亚稳和/或低温相，这是难以通过高温和/或高能处理形成的。我们在以下方面取得了成功：(1)在LiOH溶液中，可在-100℃的低温下在各种金属衬底上制备LiCoO_2薄膜。(2)为电化学活性的高温LiCoO_2相。(3)研制了一种流动型水热/电化学装置，用于制备BaTiO_3/SrTiO_3/Ti等层状膜。(4)合成了Ti、Nb和Ta的水溶性配合物，制备了含这些金属的均相双氧化物粉末。(5)一些新型层状双氧化物作为光催化剂表现出了优异的性能。(6)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纳米杂化物。(7)建立了新型双氧化物材料设计，可用于制造量子铁电材料、高锂离子导体、超导体等，这些成果将开辟材料科学与技术的新领域。

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.