High-strain actuation of lead-free perovskites : compositional effects, phenomenology and mechanism
Author(s)Soukhojak, Andrey N. (Andrey Nestorovich), 1972-
Massachusetts Institute of Technology. Dept. of Materials Science and Engineering.
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An experimental study was carried out to map the compositional dependence of electromechanical behavior and ferroelectric phase stability in the barium, zirconium-codoped sodium bismuth titanate (BNBZT) system for barium concentrations up to 18 mol.% and zirconium concentrations up to 4 mol.%. A number of polycrystalline BNBZT samples has been electromechanically tested under applied electric fields of different frequencies (0.2-47 Hz). A novel model of electromechanical response capable of describing both dynamic and static hysteresis for pure and mixed cases of ferroelectric, antiferroelectric, ferroelastic and paraelectric behavior has been developed. Major electromechanical properties of polycrystalline BNBZT have been identified and compositionally mapped. The peak of electromechanical response (d33 = 400 pC/N) has been found at the composition (Bil/2Nal/2)0.93Bao.07Zro.02Tio.9803. The compositional dependence of ferroelectric phase stability has been mapped by means of a Landau type free energy expansion. A nanodomain relaxation mechanism of frequency dependent electromechanical response of BNBZT has been suggested and is supported by optical and transmission electron microscopy.
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2002.Includes bibliographical references.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
DepartmentMassachusetts Institute of Technology. Dept. of Materials Science and Engineering.
Massachusetts Institute of Technology
Materials Science and Engineering.