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Title: Nanoscopic Study of the Polarization-Strain Coupling in Relaxor Ferroelectric and the Search for New Relaxor Materials for Transducer and Optical Applications

Abstract

SUMMARY Relaxor ferroelectrics exhibit a very unusual polarization behavior from which derive unique electrostrictive, piezoelectric and other properties. This behavior and these properties are due to the presence of nanoscale structural and polar order, the polar nanoregions (PNR), which can easily reorient under very modest external electric field, in stark contrast with conventional ferroelectrics. Moreover, when these nanoregions are aligned, their local distortions add up coherently to a macroscopic strain, hence their remarkable electrostrictive and piezoelectric properties. Initially, we demonstrated this effect in KTa1-xNbxO3 (KTN) and were able to identify the local internal symmetry of the PNR in KTN and explain their behavior under an applied electric field. We then extended the study to the more complicated lead relaxors, PbMg1/3Nb2/3O3 (PMN), PbZn1/3Nb2/3O3 (PZN) and (1-x)(PbZn1/3Nb2/3)O3-(x)PbTiO3 (PZN-PT). In particular, following the evolution of the diffuse intensity in neutron scattering and X-ray measurements, we were able to determine the evolution of the polar order from the pure PZN system to the mixed system, PZN-PT. This evolution with addition of PT, provides a physical basis for the remarkably easy polarization rotation that gives PZN-PT its unique properties for composition near the so-called morphotropic boundary (MPB). Through quasi-elastic and inelastic neutron and Raman scattering,more » we also obtained information about the local (nano)dynamics of these PNR’s. We thus identified three ranges in the evolution of the polarization with temperature: a purely dynamic range, a quasi-dynamic range when the PNR’s appear but can still reorient as “giant dipoles”, a quasi-static range when the system undergoes a series of “underlying” or partial transitions (on a mesoscopic scale) and, finally a frozen range below the last one of these transitions”. This work has provided a useful framework to describe the structural and temperature evolution from the nanoscopic to the mesoscopic polar order and even to a macroscopic polar order in the presence of an applied electric field. The results of this study also provide a physical model to explain the very strong polarization-strain coupling in these relaxors.« less

Authors:
Publication Date:
Research Org.:
Lehigh University
Sponsoring Org.:
USDOE - Office of Energy Research (ER)
OSTI Identifier:
908152
Report Number(s):
DOE/ER/45842
TRN: US200821%%320
DOE Contract Number:
FG02-00ER45842
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; DIPOLES; ELECTRIC FIELDS; NEUTRONS; POLARIZATION; ROTATION; SCATTERING; SYMMETRY; TRANSDUCERS; Transducer, Ferroelectrics, Materials

Citation Formats

J. Toulouse. Nanoscopic Study of the Polarization-Strain Coupling in Relaxor Ferroelectric and the Search for New Relaxor Materials for Transducer and Optical Applications. United States: N. p., 2007. Web. doi:10.2172/908152.
J. Toulouse. Nanoscopic Study of the Polarization-Strain Coupling in Relaxor Ferroelectric and the Search for New Relaxor Materials for Transducer and Optical Applications. United States. doi:10.2172/908152.
J. Toulouse. Thu . "Nanoscopic Study of the Polarization-Strain Coupling in Relaxor Ferroelectric and the Search for New Relaxor Materials for Transducer and Optical Applications". United States. doi:10.2172/908152. https://www.osti.gov/servlets/purl/908152.
@article{osti_908152,
title = {Nanoscopic Study of the Polarization-Strain Coupling in Relaxor Ferroelectric and the Search for New Relaxor Materials for Transducer and Optical Applications},
author = {J. Toulouse},
abstractNote = {SUMMARY Relaxor ferroelectrics exhibit a very unusual polarization behavior from which derive unique electrostrictive, piezoelectric and other properties. This behavior and these properties are due to the presence of nanoscale structural and polar order, the polar nanoregions (PNR), which can easily reorient under very modest external electric field, in stark contrast with conventional ferroelectrics. Moreover, when these nanoregions are aligned, their local distortions add up coherently to a macroscopic strain, hence their remarkable electrostrictive and piezoelectric properties. Initially, we demonstrated this effect in KTa1-xNbxO3 (KTN) and were able to identify the local internal symmetry of the PNR in KTN and explain their behavior under an applied electric field. We then extended the study to the more complicated lead relaxors, PbMg1/3Nb2/3O3 (PMN), PbZn1/3Nb2/3O3 (PZN) and (1-x)(PbZn1/3Nb2/3)O3-(x)PbTiO3 (PZN-PT). In particular, following the evolution of the diffuse intensity in neutron scattering and X-ray measurements, we were able to determine the evolution of the polar order from the pure PZN system to the mixed system, PZN-PT. This evolution with addition of PT, provides a physical basis for the remarkably easy polarization rotation that gives PZN-PT its unique properties for composition near the so-called morphotropic boundary (MPB). Through quasi-elastic and inelastic neutron and Raman scattering, we also obtained information about the local (nano)dynamics of these PNR’s. We thus identified three ranges in the evolution of the polarization with temperature: a purely dynamic range, a quasi-dynamic range when the PNR’s appear but can still reorient as “giant dipoles”, a quasi-static range when the system undergoes a series of “underlying” or partial transitions (on a mesoscopic scale) and, finally a frozen range below the last one of these transitions”. This work has provided a useful framework to describe the structural and temperature evolution from the nanoscopic to the mesoscopic polar order and even to a macroscopic polar order in the presence of an applied electric field. The results of this study also provide a physical model to explain the very strong polarization-strain coupling in these relaxors.},
doi = {10.2172/908152},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu May 31 00:00:00 EDT 2007},
month = {Thu May 31 00:00:00 EDT 2007}
}

Technical Report:

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  • Thermal maxima were computed for the polarization and strain in a polarized tetragonal ferroelectnic material. Knowledge of these maxima, related to measured values, can be used to determine the relative degrees of completeness of 90 and 180 deg switching. (auth)
  • We have fabricated magnetoelectric heterostructures by growing ferromagnetic La{sub 1-x}Ba{sub x}MnO₃ (x=0.2, 0.4) thin films on (001)-, (110)-, and (111)-oriented 0.31Pb(In{sub 1/2}Nb{sub 1/2})O₃-0.35Pb(Mg{sub 1/3}Nb{sub 1/2})O₃-0.34PbTiO₃ (PINT) ferroelectric single-crystal substrates. Upon poling along the [001], [110], or [111] crystal direction, the electric-field-induced non-180° domain switching gives rise to a decrease in the resistance and an enhancement of the metal-to-insulator transition temperature T C of the films. By taking advantage of the 180° ferroelectric domain switching, we identify that such changes in the resistance and T C are caused by domain switching-induced strain but not domain switching-induced accumulation or depletion of chargemore » carriers at the interface. Further, we found that the domain switching-induced strain effects can be efficiently controlled by a magnetic field, mediated by the electronic phase separation. Moreover, we determined the evolution of the strength of the electronic phase separation against temperature and magnetic field by recording the strain-tunability of the resistance [(ΔR/R){sub strain}] under magnetic fields. Additionally, opposing effects of domain switching-induced strain on ferromagnetism above and below 197 K for the La₀.₈Ba₀.₂MnO₃ film and 150 K for the La₀.₆Ba₀.₄MnO₃ film, respectively, were observed and explained by the magnetoelastic effect through adjusting the magnetic anisotropy. Finally, using the reversible ferroelastic domain switching of the PINT, we realized non-volatile resistance switching of the films at room temperature, implying potential applications of the magnetoelectric heterostructure in non-volatile memory devices.« less
  • This four-year project (including one-year no-cost extension) aimed to advance fundamental understanding of field-induced strain behaviors of phase transforming ferroelectrics. We performed meso-scale phase field modeling and computer simulation to study domain evolutions, mechanisms and engineering techniques, and developed computational techniques for nanodomain diffraction analysis; to further support above originally planned tasks, we also carried out preliminary first-principles density functional theory calculations of point defects and domain walls to complement meso-scale computations as well as performed in-situ high-energy synchrotron X-ray single crystal diffraction experiments to guide theoretical development (both without extra cost to the project thanks to XSEDE supercomputers andmore » DOE user facility Advanced Photon Source).« less
  • Discharge capacitors were designed based on materials with antiferroelectric (AFE) to ferroelectric (FE) field enforced transitions that had 10 times the capacitance of relaxor ferroelectric or state of the art BaTiO{sub 3} materials in the voltage range of interest. Nonlinear RLC circuit analysis was used to show that the AFE to FE materials have potentially more than 2 times the peak discharge current density capability of the BaTiO{sub 3} or lead magnesium niobate (PMN) based relaxor materials. Both lead lanthanum zirconium tin titanate (PLZST) AFE to FE field enforced phase transition materials and PMN based relaxor materials were fabricated andmore » characterized for Sandia`s pulse discharge capacitor applications. An outstanding feature of the PLZST materials is that there are high field regimes where the dielectric constant increases substantially, by a factor of 20 or more, with applied field. Specifically, these materials have a low field dielectric constant of 1,000, but an effective dielectric constant of 23,000 in the electric field range corresponding to the FE to AFE transition during discharge. Lead magnesium niobate (PMN) based relaxor materials were also investigated in this project because of their high dielectric constants. While the PMN based ceramics had a low field dielectric constant of 25,000, at a field corresponding to half the charging voltage, approximately 13 kV/cm, the dielectric constant decreases to approximately 7,500.« less