New oxybromide cobaltites with layered perovskite-related structures: 18R-Ba6Co5BrO14 and 14H-Ba7Co6BrO17

2007 ◽  
Vol 63 (4) ◽  
pp. 589-596 ◽  
Author(s):  
Matthieu Kauffmann ◽  
Pascal Roussel
Keyword(s):  
Single Crystals ◽  
Close Packing ◽  
Layered Perovskite ◽  
New Materials ◽  
Solid Reaction

Single crystals of the title compounds were prepared by solid–solid reaction using BaBr2 flux at 1373 K. The structures of these two new cobaltites were solved and refined. The two compounds are built from a close-packing of [BaO3] and [BaOBr] layers with stacking sequences (c′chhcc′)3 and (c′chhhcc′)2 for the 18R and 14H structures, respectively, which create Co3O12 trimers or Co4O15 tetramers of face-sharing octahedra connected at their extremities to isolated tetrahedra by corner-sharing. These new materials are strongly related to the 5H-Ba5Co5O14/12H-Ba0.9CoO2.6 and 10H-Ba5Co5ClO13/6H-Ba6Co6ClO16 materials, with the existence of common blocks. In Ba6Co5BrO14 and Ba7Co6BrO17, all the atoms in the vicinity of the [BaOBr] layers are disordered, whereas the rest of the structure is perfectly ordered.

Superconductivity and Magnetism in the La2 CuO4-Based Compounds

MRS Bulletin ◽  
1989 ◽  
Vol 14 (1) ◽  
pp. 33-36 ◽  
Author(s):  
Z. Fisk ◽  
S-W. Cheong ◽  
D.C. Johnston
Keyword(s):  
Single Crystals ◽  
Magnetic Measurements ◽  
Oxygen Stoichiometry ◽  
Layered Perovskite ◽  
Orthorhombic Distortion ◽  
X Ray ◽  
Bulk Superconductivity ◽  
High Oxygen Pressure ◽  
Powder Samples ◽  
Cation Ratio

La2CuO4, crystallizes in an orthorhombic distortion of the tetragonal K2NiF4 structure, a so-called layered perovskite. The important question here concerns the stoichiometry of La2CuO4 prepared by various techniques. Regarding the La and Cu sites, recent neutron diffraction studies of powders have shown that the La:Cu ratio can vary from 2:1 by ≳1% in various preparations., Single crystals have been grown variously from CuO, PbO and Li2O-B2O3 fluxes. The last two fluxes incorporate some Pb and Li, respectively, into the crystals, but the cation ratio is found to be 2:1 within the accuracy of x-ray refinement.It is also known that the oxygen stoichiometry corresponds to La2CuO4 within ≃ 1%. Extensive and precise magnetic susceptibility (χ) and other studies of powder samples showed, however, that the physical properties are extremely sensitive to < 1% changes in the oxygen content. A clear indication from electric and magnetic measurements is that the oxygen stoichiometry is always that, or richer than that, corresponding to a Mott insulator with an exactly half-filled band. Consistent with this, the stoichiometry is more properly written La2-z CuO4-y with small, positive y and z.Several groups found that bulk superconductivity above 30 K can be produced in La2CuO4 by annealing powders or single crystals at high oxygen pressure. The weight gain in this process corresponds to producing La2CuO4.13, and these authors believe the excess oxygens go in as O-2, based on iodometric titration measurements giving the amount of [Cu-O]⊥ in the sample. Jorgensen et al. found that there is a phase separation below 320 K of La2CuO4 and the O2-loaded phase in oxygen-rich samples; the latter structure is also orthorhombic, but the position of the excess oxygens could not be determined unambiguously.

New Structure Model for Lithium Nickel Batteries

2000 ◽  
Vol 623 ◽  
Author(s):  
M.A. Monge ◽  
E. Gutiérrez-Puebla ◽  
I. Rasines ◽  
J.A. Campa
Keyword(s):  
Crystal Structure ◽  
Single Crystals ◽  
Structural Type ◽  
Close Packing ◽  
The Other ◽  
Structure Model ◽  
Magnetization Measurements ◽  
Mixed Layers

AbstractAfter growing black colored single crystals of LixNi1−xO (x = 0.27) and solving its crystal structure, a model is proposed as an alternative to the structural type admitted for LixNi1−xO. The new rhombohedral cell consists of a cubic close packing of oxygens in which the alternation of two kind of mixed layers containing Li and Ni in different ratios can be detected along the c direction. This model implies a Li order incompatible with the alternation of Ni layers, one of them pure and the other containing some Li. The results of magnetization measurements look consistent with the new structural type, and reveal that LixNi1−xO behaves as mictomagnetic.

Formation of La2Zr2O7 on yttria-stabilized ZrO2(110) single crystals during vapour–solid reaction

2008 ◽  
Vol 179 (13-14) ◽  
pp. 453-457 ◽  
Author(s):  
M.A. Schubert ◽  
S. Senz ◽  
D. Hesse
Keyword(s):  
Single Crystals ◽  
Solid Reaction

Giant magnetostriction in Pr-substituted double-layered perovskite manganite La1.2Sr1.8Mn2O7 single crystals

2001 ◽  
Vol 226-230 ◽  
pp. 990-992 ◽  
Author(s):  
H Ogasawara ◽  
M Matsukawa ◽  
M Yoshizawa ◽  
M Apostu ◽  
R Suryanarayanan ◽  
...  
Keyword(s):  
Single Crystals ◽  
Layered Perovskite ◽  
Perovskite Manganite ◽  
Giant Magnetostriction

Synthesis and Growth Mechanism of Silicon Nitride Nanostructures

2005 ◽  
Vol 475-479 ◽  
pp. 1239-1242 ◽  
Author(s):  
Zhi Peng Xie ◽  
Wei You Yang ◽  
He Zhuo Miao ◽  
Li Gong Zhang ◽  
Li Nan An
Keyword(s):  
Silicon Nitride ◽  
Single Crystals ◽  
Growth Mechanism ◽  
Stacking Faults ◽  
Entire Length ◽  
New Method ◽  
Polymeric Precursor ◽  
Uniform Thickness ◽  
Solid Reaction ◽  
Solid Liquid

A new method to synthesize Si3N4 nanostructures via catalyst-assisted polymeric precursor pyrolysis is present in this article. The as-prepared nanobelts are single crystals with a uniform thickness and width along the entire length, and contain no detectable defects such as dislocations or stacking faults. The thickness and width of Si3N4 nanobelts range from 40 to 60 nm and 600 to 1200 nm, respectively, and the lengths can be up to several millimeters. The growth directions of a-Si3N4 nanobelts are [101] and [100]. A solid-liquid-solid and gas-solid reaction/crystallization is proposed for the growth of S3N4 nonastructures.

scholarly journals Impact of Layer Thickness on the Charge Carrier and Spin Coherence Lifetime in Two-Dimensional Layered Perovskite Single Crystals

2018 ◽  
Vol 3 (9) ◽  
pp. 2273-2279 ◽  
Author(s):  
Xihan Chen ◽  
Haipeng Lu ◽  
Zhen Li ◽  
Yaxin Zhai ◽  
Paul F. Ndione ◽  
...  
Keyword(s):  
Charge Carrier ◽  
Single Crystals ◽  
Layer Thickness ◽  
Layered Perovskite ◽  
Two Dimensional ◽  
Spin Coherence
Sign in / Sign up

Export Citation Format

Share Document