THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING

GEORGIA INSTITUTE OF TECHNOLOGY

Under the provisions of the regulations for the degree

DOCTOR OF PHILOSOPHY

on Thursday, May 2, 2019

12:00 PM
in Love 295

will be held the

DISSERTATION PROPOSAL DEFENSE

for

Evelyn Chin

"Radiation-Hard Relaxor-Ferroelectric Thin Films for Multi-Functional Devices"

Committee Members:

Prof. Nazanin Bassiri-Gharb, Advisor, MSE

Prof. Chaitanya Deo, NRE

Prof. Asif Khan, ECE

Prof. Mark Losego, MSE

Prof. Eric Vogel, MSE

Abstract:

Ferroelectric materials show a reversibly switchable spontaneous polarization, in addition to large dielectric, pyroelectric and piezoelectric response, making them attractive for numerous functional devices, including mechanical logic elements, optical sensors and transducers, precision positioners, energy harvesting units, and especially microelectromechanical systems (MEMS) sensors and actuators. Due to their radiation hardness, ferroelectric materials are even more attractive for use in devices for radiation-hostile environments such as in aerospace, medical physics, x-ray/high energy source measurement tools, and continuous monitoring of nuclear power plant applications.

Traditionally, lead zirconate titanate (PZT) has been the most used ferroelectric in piezoelectric MEMS. However, the increasing demand for smaller device footprint has created a need for new material systems to exceed the current standards. Of particular interest among these is (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3, PMN-PT, a relaxor-ferroelectric solid solution, which in bulk crystalline form exhibits even larger electromechanical response than ceramic PZT. Furthermore, PMN-PT’s increased chemical heterogeneity promises even greater radiation hardness with respect to PZT films. In this work, chemical solution processed PMN-PT thin films will be defect engineered through the variation of processing parameters. Total ionization dose (TID) studies will be performed by irradiating films with a 60Co source to explore the defect-defect interactions which occur within the material at radiation exposure, and their effects on the resulting functional responses. Defect-defect interactions related to interaction of ionization events with grain morphology, porosity, crystallization interfaces, and their development over time (aging) will be studied. Preliminary results have shown enhancement of functional properties in films exposed to low radiation doses, before degradation of the same at higher radiation doses is observed. A fundamental understanding of these defect-defect interactions will provide a basis for development of radiation-hard materials for the next generation of piezoMEMS devices.