湖南大学“岳麓材料青年学者论坛”第241期
报告一
题 目：A Fresh Look at Defect Structure in LISICONs using Reverse Monte Carlo Analysis of Total Neutron Scattering Data
报告人：Dr Isaac Abrahams
地 点：中四栋二楼报告厅
时 间：2023年9月3日（周日）上午9:00-10:00
主持人：杨斌 教授
邀请人：材料科学与工程学院
报告人简介：
Dr Isaac Abrahams is Head of the Department of Chemistry at Queen Mary University of London and is a former Chair of the Royal Society of Chemistry Solid State Chemistry Group. His main area of research can broadly be defined as solid state and structural chemistry with close to 250 papers published in this area. Much of his work has been in the field of energy materials, focussing on ionically conducting solids for application as electrolytes in batteries, fuel cells and gas sensors, as well as ferroelectric materials for energy storge devices. In addition to the synthesis of new materials, he has developed expertise in defect structure determination using neutron and X-ray powder diffraction techniques and in conjunction with a.c. impedance spectroscopy studies has used this to examine structure-conductivity relationships and conductivity mechanisms in a variety of materials. This work has been aided by the development of total X-ray and neutron scattering methods, where both long-range and short-range ordering can be characterized simultaneously using a Reverse Monte Carlo approach to modelling the scattering data. Although much of his work has been on crystalline solids, Dr Abrahams has made use of his background in structural inorganic chemistry in the study of amorphous solids for applications such as all-solid-state batteries and biomedical materials. Here diffraction techniques are of limited use and a variety of other structural probes such as neutron scattering, solid-state NMR spectroscopy and EXAFS are required.
报告摘要：
The LISICON structure is an important structural type that serves as a host for fast Li-ion conduction. Over 30 years ago we proposed a defect cluster model for LISICON type systems, but physical evidence for this was limited by the technology of the time. Following advances in detector technology and analysis of total neutron scattering data we are now able to re-examine this important structural type. Using reverse Monte Carlo analysis of total neutron scattering data on 7Li isotopically enriched samples of the model LISICON system Li3+xGexPl-xO4, details of the lithium-ion distribution are revealed. A detailed analysis of the defect clustering in Li3+xGexPl-xO4, has been obtained supported by 7Li and 31P solid state NMR spectroscopy. Analysis of the partial pair distribution functions Fig. 1 a,b have allowed for the identification of two independent types of defect cluster at low x-values, which then cluster together to form larger clusters at higher lithium-ion concentrations. The details of local structure revealed in this study form the basis of a better understanding of conduction mechanisms in this important class of solid electrolytes.
