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Exploring the Kinetics of Domain Switching in Ferroelectrics for Structural Applications

Citation

Wojnar, Charles Stanley (2015) Exploring the Kinetics of Domain Switching in Ferroelectrics for Structural Applications. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z9HD7SM7. http://resolver.caltech.edu/CaltechTHESIS:05302015-221358386

Abstract

The complex domain structure in ferroelectrics gives rise to electromechanical coupling, and its evolution (via domain switching) results in a time-dependent (i.e. viscoelastic) response. Although ferroelectrics are used in many technological applications, most do not attempt to exploit the viscoelastic response of ferroelectrics, mainly due to a lack of understanding and accurate models for their description and prediction. Thus, the aim of this thesis research is to gain better understanding of the influence of domain evolution in ferroelectrics on their dynamic mechanical response. There have been few studies on the viscoelastic properties of ferroelectrics, mainly due to a lack of experimental methods. Therefore, an apparatus and method called Broadband Electromechanical Spectroscopy (BES) was designed and built. BES allows for the simultaneous application of dynamic mechanical and electrical loading in a vacuum environment. Using BES, the dynamic stiffness and loss tangent in bending and torsion of a particular ferroelectric, viz. lead zirconate titanate (PZT), was characterized for different combinations of electrical and mechanical loading frequencies throughout the entire electric displacement hysteresis. Experimental results showed significant increases in loss tangent (by nearly an order of magnitude) and compliance during domain switching, which shows promise as a new approach to structural damping. A continuum model of the viscoelasticity of ferroelectrics was developed, which incorporates microstructural evolution via internal variables and associated kinetic relations. For the first time, through a new linearization process, the incremental dynamic stiffness and loss tangent of materials were computed throughout the entire electric displacement hysteresis for different combinations of mechanical and electrical loading frequencies. The model accurately captured experimental results. Using the understanding gained from the characterization and modeling of PZT, two applications of domain switching kinetics were explored by using Micro Fiber Composites (MFCs). Proofs of concept of set-and-hold actuation and structural damping using MFCs were demonstrated.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:ferroelectricity, viscoelasticity, broadband electromechanical spectroscopy, lead zirconate titanate, macro fiber composite actuator, stiffness, damping, domain switching, microstructure kinetics
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Aeronautics
Awards:Charles D. Babcock Award, 2014 ; The Donald Coles Prize In Aeronautics, 2015
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Kochmann, Dennis M.
Thesis Committee:
  • Ravichandran, Guruswami (chair)
  • Bhattacharya, Kaushik
  • Pellegrino, Sergio
  • Kochmann, Dennis M.
Defense Date:4 May 2015
Record Number:CaltechTHESIS:05302015-221358386
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:05302015-221358386
DOI:10.7907/Z9HD7SM7
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8947
Collection:CaltechTHESIS
Deposited By: Charles Wojnar
Deposited On:02 Jun 2015 15:38
Last Modified:12 Apr 2016 22:30

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