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Motivation

Motivation Sensors and actuators are used in several military functions including surveillance, reconnaissance, navigation, etc. Phase-transforming oxides, including ferroelectric materials, exhibit unique potential for multi-functionality (see figure). Scientific challenge

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Motivation

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  1. Motivation • Sensors and actuators are used in several military functions including surveillance, reconnaissance, navigation, etc. • Phase-transforming oxides, including ferroelectric materials, exhibit unique potential for multi-functionality (see figure). • Scientific challenge • One of the fundamental structural features that defines functionality in these materials are domain walls (see figure). • However, very few experiments are currently able to characterize domain wall evolution during real operating conditions of sensors and actuators (e.g., cycling fields of low amplitude). Domain Wall Ps Ps

  2. Objectives • to enhance the basic understanding which underlies the linkage between domain architectures and macroscopic properties (structure-property relationships) in bulk, phase-transforming oxides, • to explore new methods to control domain structures, and • to identify unique domain configurations with previously unrealizable properties. Macroscopic property (e.g., e-field-induced strain) V grain boundary domain domain wall motion piezoelectric effect

  3. Approach • Utilize advanced, real-time characterization techniques including in situ X-ray and neutron diffraction during thermal, electrical, mechanical, and/or magnetic field application. • These unique in situ measurements of domain wall behavior then provideinsights into materials development for enhanced functionality. • Prior state-of-the-art involved application of static electric fields at high electric field amplitudes. • Our approach involves studying domain wall motion during dynamic loading and at operation-relevant field amplitudes (often below the coercive field).

  4. Scientific Accomplishments • Time-resolved observation of domain variants {002}/{200} of tetragonal Pb(Zr,Ti)O3 ceramics demonstrate the motion of ferroelectric/ferroelastic domain walls during application of weak electric field amplitudes. • Quantitative analysis of diffraction data leads to a complete account of the contributions to the ceramic piezoelectric coefficient, d33. Relative Contributions: Macroscopic Property Measurement performed at the European Synchrotron Radiation Facility

  5. Scientific Accomplishments • The linear component of the e-field-induced lattice strains is the only component which may be intrinsic piezoelectricity (since intrinsic PE is field-independent). • Closer inspection of lattice strain measurements indicate this is not likely the intrinsic piezoelectric coefficient, but rather an elastic intergranular coupling. • Remarkably, the piezoelectric d33coefficient in this common soft PZT composition is mostly attributed to domain wall motion, not the intrinsic piezoelectric effect of the lattice. Relative Contributions: Macroscopic Property In review as a Feature Article for J. American Ceramic Society

  6. Scientific Accomplishments • Synthesis, high-resolution structural measurement, and refinement of (1-x)Na0.5Bi0.5TiO3-xBaTiO3 (BNT-xBT) piezoelectric ceramics. • Crystallographic refinement of the NBT indicates a monoclinic Cc space group, not widely-assumed R3c. • Implies complex ferroelectric/ferroelastic domain structure in BNT-based materials. May explain nanodomainsand relaxor-like behavior. • Also suggests “monoclinic” not a sufficient condition for high d33. High-resolution X-ray measurements at the Advanced Photon Source, Argonne National Laboratory

  7. Scientific Accomplishments • Acceptor-doping in Na0.5Bi0.5TiO3(BNT)-based ceramics show unexpected behavior of thermal stability. • Piezoelectric coefficient d33 as a function of temperature shows increased thermal stability for small (<1%) Fe2O3doping concentration. • Because of negligible lowering of initial (room temperature) d33, this material has a high piezoelectric coefficient at elevated temperatures. Enhanced thermal stability

  8. Transitions • The PI gave several seminars at national laboratories including: • User Science Seminar, Advanced Photon Source, Argonne National Laboratory, July 30, 2010. • Lujan Neutron Scattering Center, Los Alamos National Laboratory, July 27, 2010. • The PI participated and delivered an invited talk at a symposium organized by ARL personnel from the Aberdeen Proving Ground (XIX International Materials Research Congress, Cancun, Mexico, August 15-19, 2010.) • The PI hosted Dr. Melanie Cole from the Army Research Laboratory, Aberdeen Proving Ground, on Sept 12, 2008. She met with several faculty members and the PI and gave a departmental research seminar titled, “Compositionally Tailored Material Properties To Enable Performance Enhanced Tunable Microwave Devices.” PI Jones and PhD student Elena Aksel at Los Alamos National Laboratory

  9. PI Awards • Presidential Early Career Award for Scientists and Engineers (PECASE), Awarded January 13, 2010. • Defense Program Awards of Excellence, nominated through the Los Alamos National Laboratory and presented by Donald Cook (Deputy Administrator for Defense Programs, NNSA), August 30, 2010, “for discovering important new physics in ferroelectric ceramics used in neutron generators through clever neutron scattering experiments.” • Faculty Excellence Award, April 22, 2010. Department of Materials Science and Engineering, University of Florida. • Excellence Award for Assistant Professors, April 27, 2010, one of 10 recipients at the University of Florida. • 11 invited talks acknowledging ARO support at international conferences, national laboratories, and universities.

  10. Future Research Plans • Recent time-dependent pulse poling measurements discriminate between 180° and non-180° domain wall motion (see figure). • Use of pulsed electric fields of various durations during the electrical poling process will coerce domains into unique configurations. • This time-dependent experiment builds upon our existing electromechanical poling studies. 180° domain switching occurs first during pulsed fields Non-180° domain switching occurs last after pulsed field application

  11. Future Research Plans • Analysis of structure and resulting domain structures in BNT-xBT using high-resolution X-ray diffraction. • In situ X-ray and neutron diffraction measurements to understand origin of electromechanical behavior at x=7. • We hypothesize that high piezoelectric d33at x=7 is not related to the morphotropicphase boundary, but due to domain wall contributions (similar to PZT). • This implies that the design of high-d33 ceramics should include domain wall contributions. Peak in permittivity and d33 at x=7 W. Jo, J. L. Jones, et al., in review at J. Applied Physics

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