Date of Award
Ph.D. in Physics
Physics and Astronomy
The Acousto-Electric Impedance z of a Ferroelectric Phononic Superlattice (fps) is investigated. The analytical derivation of z and its phase reveal that both are functions of physical parameters such as the electromechanical coupling coefficient, the mechanical quality factor, the domain length and the phase velocity of the plate acoustic waves (paw). Mathematical code is produced that allows for modeling z in a two dimensional fps. It is observed that z depends on the number of domains in the fps structure. Fewer domains in the structure might minimize z or make it approach zero at certain conditions. A series of experiments is performed to investigate the impedance and its phase shift for a zx-cut periodically poled lithium niobate in the frequency range 3-4 mhz. The experimental results of studying z and its phase shift are in a good agreement with the developed theory. Experiments reveal the stopband, when an acoustic wavelength is close to a double-length of ferroelectric domain within the inversely poled structure, in which z has minima close to it. Furthermore, these experiments show that the displacement components of the acoustic mode are decoupled in the transition zone, a small frequency range that extends a few kilohertz from the boundary of the stopband, and the amplitude of those decoupled components goes to zero in that zone. The equations obtained, the computation codes developed, and the experimental investigations can be applied to the ultrasonic transducers and the field of energy harvesting
Nusierat, Ola Hassan, "Acousto-Electric Impedance Of Ferroelectric Phononic Superlattice" (2015). Electronic Theses and Dissertations. 1118.