8 research outputs found
Synchrotron x-ray Studies of Superlattice Ordering in Pb(Mg1/3Nb2/3)O3 Single Crystals Doped with PbTiO3
The temperature dependence of the superlattice reflections: a) F spots and b)
alpha spots in a lead magnesium niobate (PMN) single crystals containing 0% and
6% of PbTiO3 (PT) has been studied using synchrotron x-ray scattering
techniques. (No superlattice reflections were found in PMN doped with 32% PT).
Analysis of the temperature dependence of the alpha spots suggests the
existence of the correlated anti-parallel atomic displacements that form
nanoregions different from the chemical nanodomains. While the correlation
length is temperature independent, the magnitude of these displacements
increases on cooling below the freezing temperature Tf. Intensities of the
alpha spots above this temperature become indistinguishable from the
background. Our results show that value of Tf for each composition is very
close to the one obtained from a Vogel-Fulcher fit to the frequency dependence
of the dielectric constant maximum Tm. The relation of these correlated
anti-ferrodistortive fluctuations to polar ferroelectric nanodomains and
relaxor behavior needs further study.Comment: 10 pages, 7 figures, Conference-Fundamental Physics of Ferroelectrics
200
Hard X-ray nano-focusing with Montel mirror optics
a b s t r a c t Kirkpatrick-Baez mirrors in the Montel (or nested) configuration were tested for hard X-ray nanoscale focusing at a third generation synchrotron beamline. In this scheme, two mirrors, mounted side-by-side and perpendicular to each other, provide for a more compact focusing system and a much higher demagnification and flux than the traditional sequential K-B mirror arrangement. They can accept up to a 120 mm  120 mm incident X-ray beam with a long working distance of 40 mm and broad-bandpass of energies up to $ 30 keV. Initial test demonstrated a focal spot of about 150 nm in both horizontal and vertical directions with either polychromatic or monochromatic beam. Montel mirror optics is important and very appealing for achromatic X-ray nanoscale focusing in conventional non-extra-long synchrotron beamlines
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Size-Dependent Structural Distortions in One-Dimensional Nanostructures
No abstract.Keywords: Composites,
Inorganic synthesis,
Chalcogenides,
Binary nanoparticle superlattices,
Stability,
Misfit layer compounds,
Nanomaterials,
Nonodisperse nanocrystals,
Nanocrystal superlattices,
Gold,
Organization,
Shape,
Hybrid material
Soft phonons in
Plutonium and its alloys exhibit complex phase diagrams that imply anomalous lattice dynamics near phase stability
boundaries. Specifically, the TA [111] phonon branch in Ga-stabilized -Pu at room temperature shows a pronounced soft mode at the zone
boundary, which suggests a possible connection to the martensitic transformation from the fcc -phase to the monoclinic -phase at low temperatures. This work is a study of the lattice dynamics
of this system by X-ray thermal diffuse scattering. The results reveal
little temperature dependence of the phonon frequencies, thus indicating
that kinetic phonon softening is not responsible for this phase transition