Plenary Lecture

Ceramic Materials for Clean Energy and Environment: Precise Crystal Structure and Properties

Professor Masatomo Yashima
co-authors: Kotaro Fujii, Masahiro Shiraiwa, Keisuke Hibino
Department of Chemistry and Materials Science
Tokyo Institute of Technology


Abstract: In this plenary talk, we present the precise crystal structure and its correlation with the properties of some ceramic materials for clean energy and environment. Electron-density distributions of crystalline materials can be obtained by the maximum-entropy method (MEM) analysis of X-ray powder diffraction data and are useful to study the chemical bonding, which governs almost all the material properties. Here, we report the electron-density distributions of perovskite-type ferroelectric oxides and oxynitride photocatalyts, and of K2NiF4-type oxides. The strong covalent bonding makes the shorter and longer bond lengths, which makes the electric polarization and ferroelectricity. The covalent bonding in photocatalyts makes the band width wider, which reduces the band gap, leading to the visible-light responses. In K2NiF4-type oxides such as CaYAlO4 and LaSrAlO4, the minimum electron density of Al-apical oxygen bond is lower than that of Al-equatorial oxygen one, which makes the anisotropic thermal expansion of these materials. Neutron scattering length density distribution of crystalline materials can be obtained by the MEM analysis of neutron powder diffraction data and are useful to study the mechanism of ion diffusion and ion conduction. Here, we also report the neutron scattering length density distributions of fluorite-type, perovskite-type, K2NiF4-type oxide-ion conductors, proton conductors and lithium-cation conductors.

Brief Biography of the Speaker: Full Professor Dr. Masatomo Yashima has been a full professor in the Department of Chemistry and Materials Science at the Tokyo Institute of Technology (Tokyo Tech), from April 2011 to the present. He received a B.S. in Physics from Tsukuba University in 1986 and obtained a Ph.D. in Materials Science and Engineering from the Tokyo Institute of Technology in 1991. He was a Research Associate of Tokyo Tech from 1991-1997 and an Associate Professor of Tokyo Tech from 1997 to March 2011. His current research interests: Precise crystal structure analysis with high-temperature neutron and synchrotron powder diffraction, electron/nuclear density analysis and design of inorganic crystalline materials (ionic conductors, catalysts, ferroelectrics, photocatalysts, and biomaterials). He published over 500 papers, including over 201 original research papers (cited over 6261 times [h-index = 43] in Web of Knowledge, August 13, 2015; over 7906 times [h-index = 48] in Google Scholar, August 19, 2015). He received over twenty awards including the Award of the Ceramic Society of Japan (2009), the Award of the Crystallographic Society of Japan (2008).