Sodium bismuth titanate (NBT) ceramics are among the most promising lead-free materials for piezo... more Sodium bismuth titanate (NBT) ceramics are among the most promising lead-free materials for piezoelectric applications. This work reports the crystal structure and phase evolution of NBT and Fe-modified NBT (from 0-2 at.% Fe) using synchrotron x-ray diffraction and Raman spectroscopy, at both ambient and elevated temperatures. The crystallographic results are discussed with reference to permittivity and piezoelectric thermal depolarization measurements of the same compositions. Changes in the depolarization temperature due to Fe substitution were detected by Raman spectroscopy and were found to correlate closely with depolarization temperatures obtained from converse piezoelectric coefficient and permittivity measured in situ. The depolarization temperatures obtained from direct piezoelectric coefficient measured ex situ as well as the phase transition temperatures obtained from synchrotron x-ray diffraction were found to be at higher temperatures. The mechanisms underlying the relationship between permittivity and piezoelectric depolarization to structural transitions observed in Raman spectroscopy and x-ray diffraction are discussed.
ABSTRACT In ferroelectric materials, enhanced dielectric and piezoelectric property coefficients ... more ABSTRACT In ferroelectric materials, enhanced dielectric and piezoelectric property coefficients are found in compositions near morphotropic phase boundaries (MPBs). The material response in these compositions may be contributed by enhanced intrinsic piezoelectric distortions or increased interface motion, e.g., contributions from domain wall and interphase boundary motion, though the relative effect of these mechanisms in different materials is not yet well understood. One of the major challenges to developing this understanding is the availability and sensitivity of in situ characterization techniques, particularly during the application of cyclic electric fields of subcoercive or weak amplitude, conditions at which the property coefficients are measured. Here, we use time-resolved neutron diffraction to resolve the subtle electric-field-induced crystallographic strain mechanisms in a prototypical MPB composition, 36%BiScO3-64%PbTiO3, that contains coexisting monoclinic and tetragonal phases. We observe multiple cooperative electromechanical effects including domain wall motion in both the monoclinic and tetragonal phases, interphase boundary motion between the two phases, and electric-field-induced lattice strains. The measured effects span four orders of magnitude in frequency, facilitating the discrimination of intrinsic and extrinsic contributions to properties. Domain wall motion in the monoclinic phase dominates the response, leading to shifts of diffraction peaks as high as 2300 pm/V; these shifts reflect the field-induced changes in average pseudocubic (00h) lattice spacing of the monoclinic phase parallel to the electric field. Domain wall motion in the tetragonal phase is also readily apparent and exhibits a degree of frequency dispersion similar to that measured in both the relative permittivity and piezoelectric coefficients at similar conditions.
Although a great deal of work has been done to understand defect chemistry in "soft&... more Although a great deal of work has been done to understand defect chemistry in "soft" and "hard" PZT-based materials, there is little understanding of how defect chemistry influences the properties of lead-free piezoelectric materials. This paper reports a systematic ...
Journal of the American Ceramic Society, Jan 1, 2010
Wiley Online Library. Journal of the American Ceramic SocietyEarly View, Article first published ... more Wiley Online Library. Journal of the American Ceramic SocietyEarly View, Article first published online: 12 AUG 2010. ...
... Bismuth Titanate (Na0.5Bi0.5TiO3)-Piezoelectric Ceramic Humberto Foronda, ElenaAksel, and Jac... more ... Bismuth Titanate (Na0.5Bi0.5TiO3)-Piezoelectric Ceramic Humberto Foronda, ElenaAksel, and Jacob L. Jones College of Engineering University of Florida ... Page 2. HUMBERTO FORONDA, ELENA AKSEL, AND JACOB L. JONES ...
Bismuth-based ferroelectric ceramics are currently under intense investigation for their potentia... more Bismuth-based ferroelectric ceramics are currently under intense investigation for their potential as Pb-free alternatives to lead zirconate titanate-based piezoelectrics. The present work eval-uated the thermal depoling behavior of various compositions of Na0.5Bi0.5TiO3 ...
Bioremediation is a natural process to fight pollution where microorganisms chemically transform ... more Bioremediation is a natural process to fight pollution where microorganisms chemically transform contaminants by degradation. Understanding bacterial transport is critical to predicting bioremediation because the microorganism must be close to the contaminants. During bacterial transport ...
Sodium bismuth titanate (NBT) ceramics are among the most promising lead-free materials for piezo... more Sodium bismuth titanate (NBT) ceramics are among the most promising lead-free materials for piezoelectric applications. This work reports the crystal structure and phase evolution of NBT and Fe-modified NBT (from 0-2 at.% Fe) using synchrotron x-ray diffraction and Raman spectroscopy, at both ambient and elevated temperatures. The crystallographic results are discussed with reference to permittivity and piezoelectric thermal depolarization measurements of the same compositions. Changes in the depolarization temperature due to Fe substitution were detected by Raman spectroscopy and were found to correlate closely with depolarization temperatures obtained from converse piezoelectric coefficient and permittivity measured in situ. The depolarization temperatures obtained from direct piezoelectric coefficient measured ex situ as well as the phase transition temperatures obtained from synchrotron x-ray diffraction were found to be at higher temperatures. The mechanisms underlying the relationship between permittivity and piezoelectric depolarization to structural transitions observed in Raman spectroscopy and x-ray diffraction are discussed.
ABSTRACT In ferroelectric materials, enhanced dielectric and piezoelectric property coefficients ... more ABSTRACT In ferroelectric materials, enhanced dielectric and piezoelectric property coefficients are found in compositions near morphotropic phase boundaries (MPBs). The material response in these compositions may be contributed by enhanced intrinsic piezoelectric distortions or increased interface motion, e.g., contributions from domain wall and interphase boundary motion, though the relative effect of these mechanisms in different materials is not yet well understood. One of the major challenges to developing this understanding is the availability and sensitivity of in situ characterization techniques, particularly during the application of cyclic electric fields of subcoercive or weak amplitude, conditions at which the property coefficients are measured. Here, we use time-resolved neutron diffraction to resolve the subtle electric-field-induced crystallographic strain mechanisms in a prototypical MPB composition, 36%BiScO3-64%PbTiO3, that contains coexisting monoclinic and tetragonal phases. We observe multiple cooperative electromechanical effects including domain wall motion in both the monoclinic and tetragonal phases, interphase boundary motion between the two phases, and electric-field-induced lattice strains. The measured effects span four orders of magnitude in frequency, facilitating the discrimination of intrinsic and extrinsic contributions to properties. Domain wall motion in the monoclinic phase dominates the response, leading to shifts of diffraction peaks as high as 2300 pm/V; these shifts reflect the field-induced changes in average pseudocubic (00h) lattice spacing of the monoclinic phase parallel to the electric field. Domain wall motion in the tetragonal phase is also readily apparent and exhibits a degree of frequency dispersion similar to that measured in both the relative permittivity and piezoelectric coefficients at similar conditions.
Although a great deal of work has been done to understand defect chemistry in "soft&... more Although a great deal of work has been done to understand defect chemistry in "soft" and "hard" PZT-based materials, there is little understanding of how defect chemistry influences the properties of lead-free piezoelectric materials. This paper reports a systematic ...
Journal of the American Ceramic Society, Jan 1, 2010
Wiley Online Library. Journal of the American Ceramic SocietyEarly View, Article first published ... more Wiley Online Library. Journal of the American Ceramic SocietyEarly View, Article first published online: 12 AUG 2010. ...
... Bismuth Titanate (Na0.5Bi0.5TiO3)-Piezoelectric Ceramic Humberto Foronda, ElenaAksel, and Jac... more ... Bismuth Titanate (Na0.5Bi0.5TiO3)-Piezoelectric Ceramic Humberto Foronda, ElenaAksel, and Jacob L. Jones College of Engineering University of Florida ... Page 2. HUMBERTO FORONDA, ELENA AKSEL, AND JACOB L. JONES ...
Bismuth-based ferroelectric ceramics are currently under intense investigation for their potentia... more Bismuth-based ferroelectric ceramics are currently under intense investigation for their potential as Pb-free alternatives to lead zirconate titanate-based piezoelectrics. The present work eval-uated the thermal depoling behavior of various compositions of Na0.5Bi0.5TiO3 ...
Bioremediation is a natural process to fight pollution where microorganisms chemically transform ... more Bioremediation is a natural process to fight pollution where microorganisms chemically transform contaminants by degradation. Understanding bacterial transport is critical to predicting bioremediation because the microorganism must be close to the contaminants. During bacterial transport ...
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Papers by Elena Aksel