Understanding Inorganic Solid State Reactivity for the Design of Functional Materials

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Solid state metal oxides are widely used as functional materials due to their exceptional functional diversity and play vital roles in miniaturization and the design of highly efficient devices. This proposal requests funding for my synthesis and characterization research program concerned with the tailored design of functional solid state materials. The program has a unique focus on structure-reactivity relations in extended metal oxides. I am developing synthetic strategies using in-situ diffraction experiments capable of following solid state reactions in real time. This approach provides reaction schemes for our model systems that can be expanded to entire structural families. In addition to the discovery of intermediate phases during the synthesis we can quench and isolate those materials. My current research program clearly demonstrates the wealth of metastable functional materials that is accessible and would have been missed with high temperature solid state reactions only. I am focussing on the preparation of oxide defect structures for applications as solid state oxide electrolytes in solid state oxide fuel cells (SOFCs). SOFCs operate close to 1000°C and we are designing materials with higher oxide ion mobilities at lower temperatures. The interplay of vacancy ordered and disordered oxygen sublattices in those materials requires a deeper understanding of structure-reactivity relations, phase transitions and materials' stability under operating conditions. Using redox active metals in fluorite related structures we will investigate the creation and annihilation of oxide vacancies and their cooperative behaviour in real time. In addition we will prepare magnetic materials in order to generate spin liquids. Introducing competing interactions between magnetic moments through chemical and structural modifications allows us to probe magnetic interactions in 1, 2 and 3-dimensional lattices. We are using a wide variety of synthetic tools including low temperature topotactic reactions (fluorine insertion and solid state hydride reductions), high pressure synthesis, sol-gel and traditional high temperature solid state preparations. Our high temperature in-situ diffraction facility is capable of tracking solid state reactions in real time. Reaction pathways are clearly observable in those experiments and the results enable us to prepare bulk samples. We characterize structures in detail and evaluate their reactivities and physical properties. More advanced studies are carried out at synchrotron (APS, CLS) and neutron facilities (SNS, ILL, HFIR) using a suite of beamlines capable of following reactions at high rates, high resolution and high pressures. The proposed research program will provide unique training opportunities for students at the intersection of materials science, chemistry and physics and prepares graduates to be future leaders in Canada's research intensive economy.