The goal of this research is to elucidate the correlation between hydrogen bonding, phase transitions and electrical properties in solid acid sulfates, selenates and phosphates. These compounds exhibit numerous structure types, in which the extent and type of hydrogen bonding vary dramatically. Moreover, dramatic changes in properties accompany structural phase transitions. A broad range of experimental techniques will be employed to characterize the materials (X-ray and neutron diffraction, IR, Raman, NMR and impedance spectroscopy, and thermal analysis) and will be complimented by computational simulations to predict phase transition behavior a priori. These comprehensive studies will guide efforts to (1) control the temperature at which the transitions occur, (2) increase the conductivity in the superprotonic phases and the spontaneous polarization in the ferroelectric phases, and (3) to synthesize hypothesized structures with desirable hydrogen-bonding features. Ultimately, room temperature superprotonic conductors and ferroelectrics may be achieved. The breadth of tools to be utilized, the relative ease with which the materials can be synthesized, and the high level of public interest in energy technologies, renders this an ideal system for training the next generation of materials chemists.
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The goal of this research is to advance a fundamental understanding of a class of materials known as solid acids. This understanding will enable the optimization of properties and the development of new superprotonic conductors and ferroelectrics with enhanced performance. Proton conductors have applications in humidity and hydrogen sensors, fuel and electrolysis cells, and high energy density batteries, and ferroelectrics as capacitors and in electro-optical devices. Fuel cells, because of their relevance to a sustainable energy future, are the major drivers for this research. Solid acid compounds are a radical departure from traditional fuel cell materials. They offer potential benefits in terms of reduced complexity and cost of the fuel cell system. However, their incorporation into demonstration fuel cells is in its infancy, and consequently the materials are of too great a risk for industrial laboratories. On the other hand, the relative ease with which solid acid compounds can be synthesized as well as the broad range of characterization tools that will be employed in this work, render this project ideal for training students from the high school level through the post-doctoral scholar level. Student training ranging from short visits by high-school students, to senior theses by undergraduates, to in-depth training of doctoral students will be pursued. The combination of fundamental science, important technological consequences, and strong educational outreach justify federal support for this research.
