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LL6.04 - High Performance ITO Nanoparticles as Nanoink for Printing as a Substitute Process of Sputtering 
April 23, 2014   9:00am - 9:30am

Toyoha Mine in Sapporo had supplied In as top of world, was closed on March 31, 2006. Before that, METI (Ministry of Economy, Trade and Industry) and Tohoku University had started to discuss planning of In substitute materials development project from 2004. I claimed advantages on ITO nanoink in this committee. By sputtering process with ITO target, only 20% ITO is deposited on the substrate with 80% formed outside. ITO target of 5 times more than apparent use for film must be prepared. If we change it to printing process, the In use reduction is expected as ca 50%, considering increase in film thickness. In "Japan Rare Metal Substitute Materials Development Project" on FY2007-2011, I was responsible as Project Sub-Leader for "Reducing Indium use in transparent conducting electrodes: ITO nano-ink." The Team was Tohoku University, ULVAC, Mitsui Mining, DOWA, and Sharp. I had also attended on U.S. - Japan Roundtable on Rare Earth Elements Research and Development for Clean Energy Technologies on November 18-19, 2010 on U.S. Department of Energy Lawrence Livermore National Laboratory so that I reported the investigation of ITO nanoink for practical use.The key technology of ITO nanoink is to produce ITO nanoparticles precisely controlled in size, shape, and crystalline properties. However, ITO could not be prepared by hydrothermal synthesis because Sn-containing InOOH or In(OH)3 crystalline particles were quite stable without further conversion [Materials Trans., 50, 2808-2812 (2009)]. We have developed a novel solvothermal method to directly obtain ITO nanoparticles with cubic morphology on 2008 [Chem. Lett. 37, 1278-1279 (2008).]. Remarkably, highly crystalline cubic-shaped ITO nanoparticles with narrow size distribution were successfully prepared through one-step process from a mixed ethylene glycol solution of indium and tin salts [J. Materials Chemistry, 20, 8153-8157 (2010).] However, the monodispersity was considerably poor since the attempt to separate nucleation and particle growth was failed. Hence The Gel-Sol method was applied to ITO synthesis. The Gel-Sol method for the synthesis of monodispersed fine particles has been established in our laboratory for hematite, TiO2,[ J. Colloid Interface Science, 259, 43-52 (2003).], etc. The role of the initially formed gel is to supply a solute to growing particles with lower superstation to avoid spontaneous nucleation. As a result, monodispersed ITO nanoparticles with a cubic shape were fabricated by using quaternary ammonium hydroxide-assisted metal hydroxide organogels. The nanopartciels has perfect uniformity in size with beautiful shape, and perfect single crystalline structure including Sn [ Chem. Lett. 42, 738-740 (2013)]. As we were attempted to make thin film with ITO nanoink, it was successfully fabricated below 200 nm in thickness and the resistivity was drastically decreased below 1.0 x 10-3Ωcm after heat treatments. Now GZO nanoink as substitute of ITO has also been developed.

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Keynote Address
Panel Discussion - Different Approaches to Commercializing Materials Research
Business Challenges to Starting a Materials-Based Company
Fred Kavli Distinguished Lectureship in Nanoscience
Application of In-situ X-ray Absorption, Emission and Powder Diffraction Studies in Nanomaterials Research - From the Design of an In-situ Experiment to Data Analysis