Date of Completion

8-12-2013

Embargo Period

8-12-2013

Major Advisor

S. Pamir Alpay

Associate Advisor

George. A. Rossetti, Jr.

Associate Advisor

Pu-Xian Gao

Field of Study

Materials Science and Engineering

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

The electrothermal (electrocaloric and pyroelectric) properties of ferroelectric thin films have many applications in active solid-state cooling and infrared sensing devices. It has been shown experimentally that some thin-film ferroelectrics can produce much larger electrothermal responses than their bulk counterparts. In this work, the electrothermal properties of bulk polar dielectric (ferroelectric and incipient ferroelectric) materials and thin films have been computed using a thermodynamic methodology and the effects of electrical, thermal and mechanical boundary conditions have been illustrated. In particular, the sensitivity of pyroelectric and electrocaloric response to bias and driving fields, lateral clamping and misfit strain, thermal stresses and composition have been demonstrated. The computations show that the electrothermal behavior of ferroelectric materials for practical cooling devices depends on a complex interplay of several related sets of physical phenomena. These include the nature of the ferroelectric transition, the particular dependence of the equilibrium and transport properties on electric field and mechanical boundary constraints, and the orientation and thermal expansion coefficients of the thin film and substrate materials. The combined results provide insights concerning how the composition and orientation of the thin film material, the choice of substrate, the deposition/annealing temperature, and the electrode configuration can be used to optimize the electrothermal properties for particular applications.

Download

Share

COinS