International Symposium on Defects, Transport and Related Phenomena: Defects and Transport in Ceramics I
Sponsored by: MS&T Organization
Program Organizers: Sangtae Kim, University of California, Davis; Ruediger Dieckmann, Cornell University; Doreen Edwards, Alfred University; Manfred Martin, RWTH Aachen University; Thomas Mason, Northwestern University
Monday 2:00 PM
October 17, 2011
Room: C122
Location: Greater Columbus Convention Center
Funding support provided by: WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, Korea
Session Chair: Paul Heitjans, Leibniz University Hannover; Joachim Maier, Max-Planck-Institute
2:00 PM Invited
Charge Carrier Chemistry in Nanoscopic Materials: Joachim Maier1; 1Max-Planck-Institute
Defect chemistry is explored in space charge zones with emphasis on mesoscopic situations. After a general overview two representative examples are discussed, one with respect to conductivity and the other with respect to storage. It is shown that the effect of downsizing SrTiO3 to a nanocrystalline material of 30 nm grain size is equivalent to changing the oxygen partial pressure by 12 orders of magnitude. Experiments and calculations are in excellent agreement.The possibility of excess storage is strikingly seen in composites of Ru and Li2O, where Li2O can accommodate Li+ (but not e-) and Ru the electrons (but not Li+) giving rise to an overall Li storage, the thermodynamics of which is discussed. In an outlook limit-considerations are performed that concern the transition range between multiphase and complex phase systems.
2:40 PM Invited
Fast Li+ Ion Conductors for Solid State Batteries: Stefan Adams1; Rayavarapu Prasada Rao1; Mao-hua Chen1; 1National University of Singapore
Solid-state Li batteries (SSLBs) promise advantageous safety, cycle-life and energy density compared to conventional Li-ion batteries. Still, identifying fast ion conducting solids that are compatible with other battery components remains a challenge. Using a bond-valence based approach we screened Li+ pathways and transport mechanisms in lithium oxides and chalcogenides. Computational, structural and electrochemical studies of promising candidates focus on anion-disordered argyrodite-type thiophosphates Li6PS5X (X=Cl,Br) and garnet-related oxides Li7-xLa3Zr2-xMxO12 (M=Nb,Ta). Li6PS5X with room temperature conductivities of 10-3.1 Scm-1 was prepared by mechanical milling and characterized by neutron and X-ray diffraction. Garnet-related Li7-xLa3Zr2-xMxO12 exhibits only slightly lower conductivities but extraordinary stability in contact with Li rendering it promising for SSLBs and as separator in Li-Air or Li redox flow batteries. In both classes of compounds the combination of modeling, structural studies and performance characterization provides a way to understand the complex interplay between phase transitions, doping and dynamic Li+ redistribution.
3:20 PM Break
3:40 PM Invited
Ion Dynamics at Interfaces: Nuclear Magnetic
Resonance Studies: Paul Heitjans1; Martin Wilkening1; 1Leibniz University Hannover
Interface engineering and the study of diffusion and transport processes through and along interfacial regions play important roles in materials science and energy research. For the latter, nanostructured materials are considered to act as powerful electrodes and solid electrolytes in sustainable energy systems, such as Li ion batteries. This is due to reduced diffusion lengths achieved when going to the nanometer scale and the fact that nanocrystalline materials with an average particle size of less than about 50 nm often show an enhanced diffusivity of their charge carriers. We give examples of how solid-state nuclear magnetic resonance (NMR) spectroscopy can be used to study the diffusion parameters of Li cations located in the interfacial regions separately from those in the interior of the grains. Furthermore, challenges and perspectives of Li NMR as a tool of probing dynamic and structural properties in functional materials will be pointed out.
4:20 PM
Self Diffusion in Alpha-Al2O3: Tsubasa Nakagawa1; Nobuaki Takahashi1; Naoya Shibata2; Yuichi Ikuhara2; James D McGuffinCawley1; Arhur H Heuer1; 1Case Western Reserve University; 2The University of Tokyo
Self-diffusion in aluminum oxide (alumina, alpha-Al2O3) has been studied for 50 years because of its technological importance and fundamental interest as a model material for oxide ceramics and other refractory non-metallic substances. Despite all previous efforts, many things are still in question. One of the important issues is “the buffering effect” that appears to control oxygen diffusivity, regardless of the amount of impurities. In this study, we carefully examined self-diffusion behavior in undoped, Mg-doped and Ti-doped aluminum oxide by means of 18O and 26Al tracers using TOF-SIMS. The mechanism of the buffering will be discussed by comparing the experimental results with the defect chemistry provided by the first principles calculations.
4:40 PM
Orientation, Oxygen Activity and Temperature Dependencies of the Diffusion of Cobalt in Cobalt Orthosilicate, Co2SiO4: Qi Tang1; Ruediger Dieckmann1; 1Cornell University
To contribute to a better understanding of point defects in and defect-related transport properties of cobalt orthosilicate, Co2SiO4, the orientation-dependent diffusion of cobalt in high purity, synthetic single crystals of Co2SiO4 being in thermodynamic equilibrium with silica was experimentally studied as a function of crystallographic orientation, oxygen activity and temperature. A variety of experiments including single crystal growth, tracer diffusion and thermogravimetric studies were performed. Experimental results will be presented and conclusions made based on these results will be discussed.