References of "Kreisel, Jens 50031730"
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See detailRevised structural phase diagram of (Ba0.7Ca0.3TiO3)-(BaZr0.2Ti0.8O3)
Keeble, Dean S.; Benabdallah, Feres; Thomas, Pam A. et al

in APPLIED PHYSICS LETTERS (2013), 102(9),

The temperature-composition phase diagram of barium calcium titanate zirconate (x(Ba0.7Ca0.3TiO3)(1-x)(BaZr0.2Ti0.8O3); BCTZ) has been reinvestigated using high-resolution synchrotron x-ray powder ... [more ▼]

The temperature-composition phase diagram of barium calcium titanate zirconate (x(Ba0.7Ca0.3TiO3)(1-x)(BaZr0.2Ti0.8O3); BCTZ) has been reinvestigated using high-resolution synchrotron x-ray powder diffraction. Contrary to previous reports of an unusual rhombohedral-tetragonal phase transition in this system, we have observed an intermediate orthorhombic phase, isostructural to that present in the parent phase, BaTiO3, and we identify the previously assigned T-R transition as a T-O transition. We also observe the O-R transition coalescing with the previously observed triple point, forming a phase convergence region. The implication of the orthorhombic phase in reconciling the exceptional piezoelectric properties with the surrounding phase diagram is discussed. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4793400] [less ▲]

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See detailBifurcated Polarization Rotation in Bismuth-Based Piezoelectrics
Keeble, Dean S.; Barney, Emma R.; Keen, David A. et al

in ADVANCED FUNCTIONAL MATERIALS (2013), 23(2), 185-190

ABO3 perovskite-type solid solutions display a large variety of structural and physical properties, which can be tuned by chemical composition or external parameters such as temperature, pressure strain ... [more ▼]

ABO3 perovskite-type solid solutions display a large variety of structural and physical properties, which can be tuned by chemical composition or external parameters such as temperature, pressure strain, electric, or magnetic fields. Some solid solutions show remarkably enhanced physical properties including colossal magnetoresistance or giant piezoelectricity. It has been recognized that structural distortions, competing on the local level, are key to understanding and tuning these remarkable properties, yet, it remains a challenge to experimentally observe such local structural details. Here from neutron pair-distribution analysis, a temperature-dependent 3D atomic-level model of the lead-free piezoelectric perovskite Na0.5Bi0.5TiO3 (NBT) is reported. The statistical analysis of this model shows how local distortions compete, how this competition develops with temperature, and, in particular, how different polar displacements of Bi3+ cations coexist as a bifurcated polarization, highlighting the interest of Bi-based materials in the search for new lead-free piezoelectrics. [less ▲]

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See detailPhonon Raman scattering of RCrO3 perovskites (R = Y, La, Pr, Sm, Gd, Dy Ho, Yb, Lu)
Weber, M. C.; Kreisel, Jens UL; Thomas, P. A. et al

in Physical Review. B (2012), 85(5),

We report a systematic investigation of orthorhombic perovskite-type RCrO3 powder samples by Raman scattering for nine different rare earth Y, La, Pr, Sm, Gd, Dy, Ho, Yb, and Lu). The room-temperature ... [more ▼]

We report a systematic investigation of orthorhombic perovskite-type RCrO3 powder samples by Raman scattering for nine different rare earth Y, La, Pr, Sm, Gd, Dy, Ho, Yb, and Lu). The room-temperature Raman spectra and the associated phonon mode assignment provide reference data for structural investigation of the whole series of RCrO3 orthochromites and phonon ab-initio calculations. The assignment of the chromite spectra and comparison with Raman data on other orthorhombic perovskites allows correlating the phonon modes with the structural distortions in the RCrO3 series. In particular, two A(g) modes are identified as octahedra rotation soft modes, as their positions scale linearly with the octahedra tilt angle of the CrO6 octahedra. [less ▲]

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