Variation of Superlattice Structure of the Bi2Sr2−xCuO6-y Superconductor with Composition and Thermal History

1989 ◽  
Vol 156 ◽  
Author(s):  
B. C. Chakoumakos ◽  
J. D. Budai ◽  
B. C. Sales ◽  
Edward Sonder
Keyword(s):  
Oxygen Content ◽  
Main Peak ◽  
Formula Unit ◽  
Additional Component ◽  
X Ray Diffraction ◽  
X Ray ◽  
Superlattice Structure ◽  
Main Reflection ◽  
Structure Modulation ◽  
Weak Satellite

ABSTRACTSingle crystals of Bi2Sr2−xCuO6−y, (0.1 < x < 0.5, 0 < y < 0.5), were examined using x-ray diffraction techniques. Ditfractometer scans of θ-2θ taken normal to the cleavage planes displayed the even () reflections from = 2 to 26. Weak satellite peaks were observed on either side of each main () reflection, and their intensities relative to the main peak increased as 2θ was increased. With decreasing Sr content, the satellite peaks systematically moved away from the position of the main reflection. In contrast, the positions of the satellite peaks did not change with oxygen content which was varied by up to 0.5 oxygen atoms per formula unit. Since Tc in these crystals is sensitive to oxygen content while the superstructure modulation is not, it is unlikely that superconductivity and the structure modulation are directly related. As shown by a more detailed study of these peaks using a four-circle diffractometer and x-ray precession methods, the satellites that appear in θ-2θ scans are actually the mosaic tails of relatively intense superstructure peaks, positioned off from c* in the b* direction of reciprocal space. Depending on the Sr content of the crystals, generally incommensurate modulations were found with the superstructure periodicity ranging between ˜1/5b* + 0.29c* and ˜1/5b* + 0.65c*. The modulation in Bi2Sr2−xCuO6−y has two components. The component along the b* direction is similar to the superstructure observed in Bi2Sr2CaCu2O7 crystals and thus is probably due to the mismatch between the Bi2O2 layer and the CuO2 layer. The additional component along c* may be due to the ordering of Sr vacancies.

Antiphase Boundaries in Ordered Ni3FE Crystals

1969 ◽  
Vol 27 ◽  
pp. 62-63
Author(s):  
Y. H. Liu
Keyword(s):  
Domain Size ◽  
Antiphase Domain ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hardening Mechanism ◽  
Superlattice Structure ◽  
Disordered Phase ◽  
Domain Boundaries ◽  
Atomic Scattering ◽  
The Difference

Ordered Ni3Fe crystals possess a LI2 type superlattice similar to the Cu3Au structure. The difference in slip behavior of the superlattice as compared with that of a disordered phase has been well established. Cottrell first postulated that the increase in resistance for slip in the superlattice structure is attributed to the presence of antiphase domain boundaries. Following Cottrell's domain hardening mechanism, numerous workers have proposed other refined models also involving the presence of domain boundaries. Using the anomalous X-ray diffraction technique, Davies and Stoloff have shown that the hardness of the Ni3Fe superlattice varies with the domain size. So far, no direct observation of antiphase domain boundaries in Ni3Fe has been reported. Because the atomic scattering factors of the elements in NijFe are so close, the superlattice reflections are not easily detected. Furthermore, the domain configurations in NioFe are thought to be independent of the crystallographic orientations.

Synthesis and Photoluminescence of Amorphous Ca5Ge2O9 Nanowires

2008 ◽  
Vol 8 (12) ◽  
pp. 6376-6380 ◽  
Author(s):  
Meng-Yen Tsai ◽  
Chung-Yi Yu ◽  
Tsong-Pyng Perng
Keyword(s):  
Inductively Coupled Plasma ◽  
Vapor Condensation ◽  
Mass Spectrometric ◽  
Main Peak ◽  
X Ray Diffraction ◽  
One Dimensional ◽  
X Ray ◽  
Inductively Coupled ◽  
Violet Luminescence ◽  
New Thinking

A new method to prepare amorphous Ca5Ge2O9 nanowires is demonstrated in the present study. Germanium nanoparticles with the size ranging from 10 to 50 nm were first prepared by a vapor condensation technique. Upon immersing the nanoparticles in Ca(OH)2 aqueous solution, hydrated Ca5Ge2O9 nanowires were formed rapidly. The phase was determined by X-ray diffraction, and the stoichiometry of Ca:Ge was further confirmed by energy-dispersive X-ray spectroscopic and inductively coupled plasma-mass spectrometric analyses. The diameter of nanowires varied from several tens to more than 100 nm, and the length increased with aging time up to the completion of reaction. After dehydrating at 400 °C, the nanowires became amorphous, and the stoichiometry of Ca:Ge remained unchanged. A blue-violet luminescence was detected from these amorphous nanowires. The emission band distributed from 300 to 550 nm, with the main peak locating at 380 nm. Ge-associated luminescence centers are proposed to be responsible for this emission. The formation of amorphous Ca5Ge2O9 nanowires may provide a new thinking to prepare other kinds of amorphous one-dimensional nanomaterials.

Synthesis and Characterization of Srilankite Nanowires

2008 ◽  
Vol 8 (3) ◽  
pp. 1481-1488 ◽  
Author(s):  
Marguerite Germain ◽  
Philip Fraundorf ◽  
Sam Lin ◽  
Elena A. Guliants ◽  
Christopher E. Bunker ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Synthesis And Characterization ◽  
X Ray Diffraction ◽  
X Ray ◽  
Molar Ratios ◽  
Superlattice Structure ◽  
Titanate Nanowires ◽  
Alkaline Conditions ◽  
Diffraction Patterns

We describe the synthesis and characterization of srilankite (Ti2ZrO6) nanowires. The nanowires are produced via hydrothermal synthesis with a TiO2/ZrO2 mixture under alkaline conditions. The zirconium titanate nanowires have median diameters of 60 nm and median lengths of 800 nm with the 〈022〉 axis along the length of the nanowire. Electron microscopy, energy dispersive X-ray spectroscopy, powder X-ray diffraction, and electron diffraction are used to characterize the phases and compare nanowires produced with varying molar ratios of Ti and Zr. Electron diffraction patterns produced from single nanowires show highly crystalline nanowires displaying a compositional-ordering superlattice structure with Zr concentrated in bands within the crystal structure. This is in contrast to naturally occurring bulk srilankite where Zr and Ti are randomly substituted within the crystal lattice. Streaking is observed in the electron diffraction patterns suggesting short-range ordering within the superlattice structure.

(Ph4P)2 Mn2Br6 und (Ph3PCH2Ph)2Mn2I6 (Ph = C6H5) / (Ph4P)2Mn2Br6 and (Ph 3PCH2Ph)2Mn2I6 (Ph = C6H5

1988 ◽  
Vol 43 (2) ◽  
pp. 171-174 ◽  
Author(s):  
Siegfried Pohl ◽  
Wolfgang Saak ◽  
Peter Stolz
Keyword(s):  
Single Crystal ◽  
Diffraction Data ◽  
Unit Cell ◽  
Formula Unit ◽  
X Ray Diffraction ◽  
Triclinic Space Group ◽  
X Ray ◽  
Bond Lengths ◽  
The Mean ◽  
The Difference

(Ph4P)2Mn2Br6 (1) and (Ph3PCH2Ph)2Mn2I6 (2) were prepared from the reaction of manganese dihalide with the corresponding phosphonium halide in CH2Cl2.The structures of 1 and 2 were determined from single crystal X-ray diffraction data.Both compounds crystallize in the triclinic space group P 1 with one formula unit per unit cell.1:a = 998.1(1), b = 1005.7(1), c = 1313.3(2) pm, α = 108.51(1), β = 94.25(1), γ = 100.36(1)°.2: a = 1058.6(2), b = 1236.3(2), c = 1248.4(3) pm, α = 63.53(1), β = 74.15(1), γ = 74.65(1)°.The structures of 1 and 2 exhibit discrete, dimeric anions formed by the fusion of two identical tetrahedral-like units with a common halogen-halogen edge. The mean Mn-Hal bond lengths were found to be 251.8 pm (Mn-Br) and 272.2 pm (Mn-I). The difference between the bridging and terminal Mn-Hal bond lengths is about 12-13 pm in both compounds

Nitrosodisulphonates and hydroxylamine-N,N-disulphonates. V. A potassium salt of hydroxylamine-N,N-disulphonic acid with a displacive superlattice structure

1988 ◽  
Vol 66 (4) ◽  
pp. 655-661
Author(s):  
John S. Rutherford ◽  
Beverly E. Robertson ◽  
Richard J. Guttormson ◽  
David B. Russell
Keyword(s):  
Potassium Salt ◽  
Average Length ◽  
Structural Complexity ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
X Ray ◽  
Superlattice Structure ◽  
Base Mismatch ◽  
Disulphonic Acid ◽  
Integrated Intensities

The structure of the potassium salt of hydroxylamine-N,N-disulphonate, with the formula K5HN2S4O14•H2O, has been determined by X-ray diffraction. The crystals are triclinic, a = 14.011(6), b = 16.118(9), c = 11.867(6) Å, α = 103.28(6), β = 106.76(3), γ = 86.38(3)°, [Formula: see text] with Z = 6. The integrated intensities of 8694 independent reflections were measured on a four-circle diffractometer, 5236 of which were used in the refinement to give a final least-squares weighted residual of 0.107 and a conventional R factor of 0.081.The structure forms a six-fold derivative lattice, which arises by small displacements (ca. 0.2 Å) of the atom positions from an average structure which is triclinic with Z = 1. This results in three very short H bonds, average length 2.46 Å, which link the three independent anion-dimers, being symmetry-free in this structure. Other bond lengths and angles in the anions are very similar to those in the Rb salt. The K+ ions show 8, 9, and 10 coordination, in a number of different polyhedral types. The three independent water molecules are each coordinated to three totally distinct K+ ions, and are linked to the anions by weak H bonds. The structural complexity may be explained in terms of a Lewis acid–base "mismatch" of the cations and anions present.

Influence of Oxygen Content in Oriented LaCoO3[sub -δ] Thin Films: Probed by X-ray diffraction and Raman Spectroscopy

2011 ◽  
Author(s):  
D. K. Mishra ◽  
Anju Ahlawat ◽  
V. G. Sathe ◽  
Alka B. Garg ◽  
R. Mittal ◽  
...  
Keyword(s):  
Thin Films ◽  
Raman Spectroscopy ◽  
Oxygen Content ◽  
X Ray Diffraction ◽  
X Ray
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