Understanding and Manipulating Charge and Entropy Flows in Layered Structured Transition Metal Dichalcogenides by and for Thermoelectricity: A Multi-scale Materials Chem. Approach

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TECHNICAL SUMMARY:The primary objective of this project, sponsored by the Solid State and Materials Chemistry program of the Division of Materials Research, is to understand and tailor the charge and entropy flows in layer-structured transition metal dichalcogenides (LTMDs) by studying their thermoelectric (TE) properties in totality for higher TE performance. The structural simplicity of LTMDs facilitates an understanding of charge and entropy flows, while the chemical versatility allows for manipulating their interplay. In this project, the "material template", LTMDs, will be subject to multi-scale restructuring via substitutional doping, intercalation-deintercalation, exfoliation, and hot deformation, followed by detailed studies of crystal and defect chemistry, microstructures, and TE properties. A compelling topic involves mobile ion intercalated LTMDs, in which quasi-two-dimensional multi-scale ionic microstructures evolve under a thermal gradient (i.e. the Sorét effect). Spark plasma sintering, emission Mössbauer spectroscopy, parallel thermal conductivity measurements, and hot-stage micro-Raman spectroscopy will be used to facilitate the proposed research.NON-TECHNICAL SUMMARY:This project will take a course of materials-by-discovery and materials-by-design in layer structured transition metal dichalcogenides (LTMDs). The scientific results emanated from this project will provide key insights in order to bridge two different realms of energy-related materials research in thermoelectric materials (electronic conductors for direct heat-to-electricity energy conversion) and electrolyte materials (ionic conductors for energy storage in batteries). The research plan builds on a close collaboration between doctorate granting/research universities, non-doctorate granting universities, and national labs. The research activities are integrated with a comprehensive education plan to serve the nation's needs in energy-related materials research. The students involved in this project will learn to use various equipment, facilities, and techniques in materials synthesis, materials chemistry processing, and materials characterization. A major part of the training will be on single crystal growth, a discipline that "not only led to the advancement of science but also made a direct and significant contribution to society in general" as emphasized by the National Research Council. Furthermore, the dissemination of scientific results to the broader public through lectures, science fairs, and classroom demonstrations will enhance scientific understanding and hopefully stimulate new ideas in energy-related material research.