Probing the Chemistry and Physics of Complex Interfaces in Transition Metal Oxides for Energy-related Applications

09:00 AM - 10:00 AM
Xiang Gao, Japan Fine Ceramics Center, Nagoya
Materials Science and Technology Division Seminar
Chemical and Materials Sciences Building (4100), Room J-302
Email: Ho Nyung Lee

It has been famously said that the interface is the device. This is particularly true for transition metal oxide (TMO) materials, because they offer an amazing variety of electronic and ionic properties and phenomena that are frequently controlled by the nature of the interfaces. Many of these phenomena originate from or are closely related to lattice deformation and nanoscale electronic and maganetic ordering. Oxide interfaces whose symmetry constraints differ from the bulk crystal can be used to manipulate device properties and even generate new phenomena. However, by their very nature, oxide interfaces are usually complex, with different structures, oxidation states and impurity concentrations, for example, than in the bulk crystal. Precise understanding of these interfacial properties and processes remains challenging but promises huge rewards in terms of new technological discoveries and applications. Recent advances in scanning transmission electron microscopy (STEM) make it possible to characterize interfaces in unprecedented detail. Aberration-corrected and monochromated electron beams used in STEMs allow local atom arrangements, strain fields and chemical bonding states of both light and heavy elements to be determined with high spatial and high energy resolutions. In this talk, I will present results obtained using state-of-the-art angle-resolved STEM and monochramated EELS to analyze various interfaces in TMOs, including perovskite-structured La2/3-xLi3xTiO3 and La1/3-xLi3xNbO3, spinel-structured LiMn2O4 and LiNi0.45Fe0.05Mn1.45Ti0.05O4, and olivine-structured LiCoPO4, prepared either as powders or thin epitaxial films. All of these are candidate electrolyte and electrode materials for solid-state thin-film Li-ion batteries. Such analyses reveal the critical influence of interfaces on the macroscopic properties of these technologically important materials. Application of these techiques can be expected to provide novel insights into the interface structures and crystal chemistry behavior of other TMO materials, including photovoltaics, photocatalysts, thermoelectrics, multiferroics, and so on.


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