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Title: Ferroelectrics : models and applications
Author: Huber, J. E.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1998
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A systematic method for selecting actuators (devices which produce a controlled force or displacement) for a given application is developed. Performance characteristics for several classes of actuator are presented in a graphical form which allows the characteristics of the actuator to be matched to the requirements of tasks. Some conclusions are drawn regarding the suitability of ferroelectric actuators for various tasks, and the opportunity offered by the non-linear, high force and high displacement regime of behaviour in ferroelectrics. A micromechanical constitutive model for the non-linear behaviour of ferroelectric crystals is developed. This model is based on the observation that ferroelectric transformations may be treated as if they were crystal slip systems, which allows conventional crystal plasticity models to be extended to the ferroelectric case. Expressions for the instantaneous tangent properties of a ferroelectric crystal are derived. The behaviour of the constitutive model is explored. The strain and polarization response to calculated for a single crystal subjected to mechanical and electrical loading; the evolution of single crystal yield surfaces is determined. A self-consistent scheme is used in conjunction with the constitutive model to produce estimates of the response of a ferroelectric polycrystal to electrical and mechanical loading. Expressions are derived for self-consistent estimates of the instantaneous tangent properties of a ferroelectric polycrystal. Self-consistent calculations of dielectric hysteresis and "butterfly" hysteresis are compared with experimental measurements made on a commercial Lead Zirconate Titanate ceramic. Predictions of the development of a cornered ferroelectric yield surface under loading are given.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available