Browsing by Author "Glaum, J"

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    Domain fragmentation during cyclic fatigue in 94%Bi(1/2)Na(1/2)TiO3-6%BaTiO3.
    (American Institute of Physics, 2012-01-01) Simons, H; Glaum, J; Daniels, JE; Studer, AJ; Liess, A; Rodel, J; Hoffman, M
    The fatigue of the lead-free piezoceramic 94%(Bi1/2Na1/2)TiO3-6%BaTiO3 was investigated under bipolar electric fields. Degradation of the polarization, strain, and permittivity was measured during the fatigue process, and correlated with structural data measured at incremental points in the fatigue process using neutron diffraction. The results suggest a two-stage fatigue mechanism whereby, following a field-induced phase transformation to a poled ferroelectric state, the domain structure becomes progressively fragmented by a repetitive process of domain wall pinning and subdivision. © 2012, American Institute of Physics.
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    Electric-field-induced phase transitions in co-doped Pb(Zr1−xTix)O3 at the morphotropic phase boundary
    (Taylor and Francis Online, 2014-02-28) Franzbach, DJ; Seo, YH; Studer, AJ; Zhang, Y; Glaum, J; Daniels, JE; Bencan, A; Malic, B; Webber, KG
    The strain- and polarization-electric field behavior was characterized at room temperature for Pb0.98Ba0.01(Zr1−xTix)0.98Nb0.02O3, 0.40  x  0.60. The investigated compositions were located in the vicinity of the morphotropic phase boundary, giving insight into the influence of crystal structure on the hysteretic ferroelectric behavior. The remanent strain of particular compositions is shown to be larger than theoretically allowed by ferroelectric switching alone, indicating the presence of additional remanent strain mechanisms. A phenomenological free energy analysis was used to simulate the effect of an applied electric field on the initial equilibrium phase. It is shown that electric-field-induced phase transitions in polycrystalline ferroelectrics can account for the experimental observations. The experimental and simulation results are contrasted to neutron diffraction measurements performed on representative compositions in the virgin and remanent states. © 2014, National Institute for Materials Science.
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    Origin of large recoverable strain in 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 near the ferroelectric-relaxor transition
    (America Institute of Physics, 2013-02-11) Simons, H; Daniels, JE; Glaum, J; Studer, AJ; Jones, JL; Hoffman, M
    Piezoceramics of composition 0.94(Bi(0.5)Na(0.5))TiO(3)-0.06BaTiO(3) demonstrate large recoverable strain at elevated temperature (T > 75 degrees C), which is absent at room temperature. In situ neutron diffraction was used to measure changes in the crystallographic and domain structures during electric field application at temperatures ranging from 25 degrees C to 100 degrees C. Quantitative evaluation of the ferroelastic domain volume fraction in the field-induced phases enabled calculation of the strain contribution from non-180 degrees domain switching. The large recoverable strain is shown to be associated with the reversible nature of the phase transformation. These findings have implications to additional BNT-xBT-based composition and other relaxor ferroelectrics. © 2013, American Institute of Physics
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    Tailoring the piezoelectric and relaxor properties of (Bi1/2Na1/2)TiO3-BaTiO3 via zirconium doping
    (John Wiley and Sons, 2013-04-25) Glaum, J; Simons, H; Acosta, M; Hoffman, M
    This article details the influence of zirconium doping on the piezoelectric properties and relaxor characteristics of 94(Bi1/2Na1/2)TiO3–6Ba(ZrxTi1−x)O3 (BNT–6BZT) bulk ceramics. Neutron diffraction measurements of BNT–6BZT doped with 0%–15% Zr revealed an electric-field-induced transition of the average crystal structure from pseudo-cubic to rhombohedral/tetragonal symmetries across the entire compositional range. The addition of Zr up to 10% stabilizes this transition, resulting in saturated polarization hysteresis loops with a maximum polarization of 40 μC/cm2 at 5.5 kV/mm, while corresponding strain hysteresis measurements yield a maximum strain of 0.3%. With further Zr addition, the ferroelectric order is progressively destabilized and typical relaxor characteristics such as double peaks in the current density loops are observed. In the strain hysteresis, this destabilization leads to an increase of the maximum strain by 0.05%. These changes to the physical behavior caused by Zr addition are consistent with a reduction of the transition temperature TF-R, above which the field-induced transformation from the relaxor to ferroelectric state becomes reversible. © 2013, The American Ceramic Society.