Radiation defects in heavy ion-irradiated nickel at low temperature by X-ray diffuse scattering

The crystal structure of the low-temperature form of barium metagermanate (BaGeO3) has been determined from laboratory X-ray powder diffraction data collected at 298.5 (5) K. The structure was found to consist of alternating layers of Ba cations and [GeO3]3 rings, and is closely related to pseudo-wollastonite. The rings show a twofold positional disorder owing to stacking faults. The stacking is not random, but can be rationalized by a twinning mechanism mapping the two non-congruent enantiomorphic polytypes of the structure onto each other. This model also explains the diffuse scattering and twinning observed in SAED and HRTEM, as well as the size and strain-like broadening effects found in the XRPD pattern.

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POLARON ORDERING IN FERROMAGNETIC COLOSSAL MAGNETORESISTIVE OXIDES

International Journal of Modern Physics B ◽

10.1142/s021797920000426x ◽

2000 ◽

Vol 14 (29n31) ◽

pp. 3711-3718 ◽

Cited By ~ 1

Author(s):

L. VASILIU-DOLOC ◽

R. OSBORN ◽

S. ROSENKRANZ ◽

J. MESOT ◽

J. F. MITCHELL ◽

...

Keyword(s):

Low Temperature ◽

Neutron Scattering ◽

Wave Vector ◽

Diffuse Scattering ◽

Short Range ◽

Metal Insulator Transition ◽

Metal Insulator ◽

Charge Delocalization ◽

X Ray ◽

Colossal Magnetoresistive

We review our recent x-ray and neutron scattering studies that reveal static diffuse scattering due to polarons in the paramagnetic phase of the colossal magnetoresistive manganites La 2-2x Sr 1+2x Mn 2 O 7, with x=0.40 and 0.44. We show that the polarons exhibit short-range incommensurate correlations that grow with decreasing temperature, but disappear abruptly at the combined ferromagnetic and metal-insulator transition in the x=0.40 system because of the sudden charge delocalization, while persisting at low temperature in the antiferromagnetic x=0.44 system. The "melting" of the polaron ordering as we cool through TC occurs with the collapse of the polaron scattering itself in the x=0.40 system. The polaron order is characterized by an ordering wave vector q=(0.3,0,1) that is almost independent of x for x≥0.40, and is consistent with a model of disordered stripes.

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X-ray diffuse scattering study of the low-temperature microdomains in silver β-alumina

Acta Crystallographica Section A ◽

10.1107/s0567739476000557 ◽

1976 ◽

Vol 32 (2) ◽

pp. 250-255 ◽

Cited By ~ 22

Author(s):

J. P. Boilot ◽

J. Thery ◽

R. Collongues ◽

R. Comès ◽

A. Guinier

Keyword(s):

Low Temperature ◽

Diffuse Scattering ◽

X Ray ◽

Scattering Study

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High pressure and low temperature cell for x‐ray diffuse scattering studies

Review of Scientific Instruments ◽

10.1063/1.1136284 ◽

1980 ◽

Vol 51 (6) ◽

pp. 836-841 ◽

Cited By ~ 9

Author(s):

A. H. Moudden ◽

L. Gatebois ◽

F. Denoyer ◽

M. Lambert

Keyword(s):

High Pressure ◽

Low Temperature ◽

Diffuse Scattering ◽

X Ray

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Axial Observation of X-Ray Spectra from a Beam-Foil Source

International Astronomical Union Colloquium ◽

10.1017/s0252921100108048 ◽

1988 ◽

Vol 102 ◽

pp. 339-342

Author(s):

J.M. Laming ◽

J.D. Silver ◽

R. Barnsley ◽

J. Dunn ◽

K.D. Evans ◽

...

Keyword(s):

Spectral Resolution ◽

Heavy Ion ◽

Ion Beams ◽

Beam Axis ◽

Doppler Broadening ◽

X Ray ◽

Beam Foil

AbstractNew observations of x-ray spectra from foil-excited heavy ion beams are reported. By observing the target in a direction along the beam axis, an improvement in spectral resolution, δλ/λ, by about a factor of two is achieved, due to the reduced Doppler broadening in this geometry.

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Low temperature x-ray microanalysis of frozen-hydrated tobacco leaves

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100111537 ◽

1984 ◽

Vol 42 ◽

pp. 284-285

Author(s):

S. Edith Taylor ◽

Patrick Echlin ◽

May McKoon ◽

Thomas L. Hayes

Keyword(s):

Low Temperature ◽

Lemna Minor ◽

Root Tips ◽

Tobacco Leaves ◽

X Ray ◽

Whole Cells ◽

Carbon Coated ◽

The Right ◽

Beam Currents ◽

The University

Low temperature x-ray microanalysis (LTXM) of solid biological materials has been documented for Lemna minor L. root tips. This discussion will be limited to a demonstration of LTXM for measuring relative elemental distributions of P,S,Cl and K species within whole cells of tobacco leaves.Mature Wisconsin-38 tobacco was grown in the greenhouse at the University of California, Berkeley and picked daily from the mid-stalk position (leaf #9). The tissue was excised from the right of the mid rib and rapidly frozen in liquid nitrogen slush. It was then placed into an Amray biochamber and maintained at 103K. Fracture faces of the tissue were prepared and carbon-coated in the biochamber. The prepared sample was transferred from the biochamber to the Amray 1000A SEM equipped with a cold stage to maintain low temperatures at 103K. Analyses were performed using a tungsten source with accelerating voltages of 17.5 to 20 KV and beam currents from 1-2nA.

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Bulk standards for low-temperature biological x-ray microanalysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100111525 ◽

1984 ◽

Vol 42 ◽

pp. 282-283

Author(s):

P. Echlin ◽

M. McKoon ◽

E.S. Taylor ◽

C.E. Thomas ◽

K.L. Maloney ◽

...

Keyword(s):

Phase Separation ◽

Low Temperature ◽

Analytical Method ◽

Salt Solutions ◽

Absolute Concentration ◽

Cooling Process ◽

X Ray ◽

The Absolute ◽

Analytical Procedures ◽

Electrical Conductors

Although sections of frozen salt solutions have been used as standards for x-ray microanalysis, such solutions are less useful when analysed in the bulk form. They are poor thermal and electrical conductors and severe phase separation occurs during the cooling process. Following a suggestion by Whitecross et al we have made up a series of salt solutions containing a small amount of graphite to improve the sample conductivity. In addition, we have incorporated a polymer to ensure the formation of microcrystalline ice and a consequent homogenity of salt dispersion within the frozen matrix. The mixtures have been used to standardize the analytical procedures applied to frozen hydrated bulk specimens based on the peak/background analytical method and to measure the absolute concentration of elements in developing roots.

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