Doctor of Philosophy (Ph.D.)
The microscopic motion of hydrogen in solid oxides plays an important role in defect migration and reaction processes. Understanding the vibrational dynamics associated with both hydrogen-oxygen (O-H) bonds and the surrounding ionic environment allows one to better characterize these fundamental interactions. This thesis presents a comprehensive investigation into the vibrational decay dynamics of O-H and O-D stretch modes in crystalline oxides using time-resolved infrared pump-probe spectroscopy.;Measurements of the vibrational lifetimes of hydrogen related local modes in potassium tantalate (KTaO3) and titanium dioxide (TiO2 ) show that the localized O-H vibration is very closely tied to proton transport. In KTaO3 we find the lifetimes to be on the order of a few hundred picoseconds and determine that the vibrational decay is due to a lattice-assisted tunneling process. Furthermore, we identify the assisting phonon and extract the excited-state tunneling rate. In TiO2 we measure the lifetimes at only a few picoseconds. Here, the decay can be described by a classical hopping process. In both cases the absorption-stimulated transfer rate is found to be dramatically larger than spontaneous or thermally activated proton transfer.;These studies provide valuable information regarding the details and fundamentals of hydrogen-lattice interactions in solid oxides. Such insight is valuable for better understanding the role of hydrogen in materials important for a variety of applications ranging from optoelectronics to alternative energy technologies.
© The Author
Spahr, Erik J., "Microscopic Dynamics and Transport of Hydrogen in Proton Conducting Oxides" (2011). Dissertations, Theses, and Masters Projects. Paper 1539623579.