Structural characterization of La2−xMxCuO4 (M = Sr,Ba) samples by synchrotron x-ray and neutron powder diffraction techniques

1988 ◽  
Vol 3 (6) ◽  
pp. 1327-1335 ◽  
Author(s):  
D. E. Cox ◽  
S. C. Moss ◽  
R. L. Meng ◽  
P. H. Hor ◽  
C. W. Chu
Keyword(s):  
High Resolution ◽  
Rietveld Refinement ◽  
Powder Diffraction ◽  
Structural Characterization ◽  
Neutron Powder Diffraction ◽  
Superconducting Properties ◽  
X Ray Diffraction ◽  
Neutron Data ◽  
X Ray

High-resolution synchrotron x-ray powder diffraction studies on samples of La2−xMxCuO4 (M = Sr,Ba) prepared by standard ceramic techniques show that macroscopic compositional inhomogeneities may exist that are unlikely to be revealed by conventional x-ray diffraction methods. Rietveld refinement of neutron data collected at 200, 50, and 11 K from one such sample, nominally La1.8Sr0.2CuO4, gave satisfactory fits to a tetragonal structure of K2NiF4 type at all three temperatures. However, careful individual peak fits revealed that part of the sample transforms to orthorhombic between 200 and 50 K. It is suggested that this multiphase character has an important influence on the superconducting properties.

scholarly journals STRUCTURAL CHARACTERIZATION OF 2-AMINO-2-OXOACETIC ACID BY X-RAY POWDER DIFFRACTION AND QUANTUM CHEMISTRY

2019 ◽  
Vol 16 (33) ◽  
pp. 516-523
Author(s):  
G. E. DELGADO ◽  
L. M. BELANDRIA ◽  
M. GUILLEN ◽  
A.. J. MORA ◽  
L. E. SEIJAS
Keyword(s):  
Hydrogen Bonds ◽  
Single Crystal ◽  
Structural Study ◽  
Powder Diffraction ◽  
Structural Characterization ◽  
Structure Determination ◽  
Spectroscopic Techniques ◽  
X Ray Diffraction ◽  
X Ray

2-amino-2-oxoacetic acid, carbamoyl formic acid, or oxamic acid is an active pharmaceutical ingredient (API) of great importance mainly because is an inhibitor of lactic dehydrogenase (LDH). It acts as an inhibitor to the metabolic pathways of the tumor cells and exhibited significant anticancer activity against nasopharyngeal carcinoma (NPC) cells in vitro and can be considered as a potential drug for the treatment of type 2 diabetes. Also, this compound could be used as a building block in the design of supramolecular architectures based on hydrogen bonds through the complimentary hydrogen-bond functionalities of the carbonyl and amide functional groups present. Single-crystal X-ray diffraction is the most powerful technique for crystal structure determination of small molecules. However, for several materials, including oxamic acid, it could be complicated to grow single crystals of suitable size and quality that make them appropriated to structure analysis. For this reason, the structural study was conducted with powder X-ray diffraction which is a process significantly more challenging than structure determination from single-crystal data. Oxamic acid has been characterized by FT-IR and NMR spectroscopic techniques, thermal TGA-DSC analysis, semi-empirical PM7 calculations, and X-ray powder diffraction. The title compound crystallizes in the monoclinic system with space group Cc, Z=4, and unit cell parameters a= 9.4994(4) Å, b= 5.4380(2) Å, c= 6.8636(3) Å, b= 107.149(2)°, V= 338.79(2) Å3. The molecule has a trans conformation. The molecular structure and crystal packing are stabilized mainly by intra- and intermolecular O--H···O and N--H···O hydrogen bonds. The structural characterization of this type of API compound is important to understand its mechanisms of action due to its considerable biological effects. In particular, for oxamic acid, this structural study would allow subsequent examination of its medicinal properties as an antitumor and antidiabetic agent.

Compositional and Structural Characterization of Heterostructure InGaN-Based Light-Emitting Diode by High Resolution X-Ray Diffraction

2012 ◽  
Vol 620 ◽  
pp. 22-27 ◽  
Author(s):  
Ahmad Hadi Ali ◽  
Ahmad Shuhaimi ◽  
Hassan Zainuriah ◽  
Yushamdan Yusof
Keyword(s):  
High Resolution ◽  
Dislocation Density ◽  
Structural Characterization ◽  
Light Emitting Diode ◽  
X Ray Diffraction ◽  
Rocking Curve ◽  
Light Emitting ◽  
X Ray ◽  
Multi Quantum Well

This paper focuses on the compositional and structural characterization of InGaN-based light-emitting diode (LED) using high resolution x-ray diffraction (HRXRD) system. The LED was epitaxially grown on Si (111) substrate that comprises of In0.11Ga0.89N multi-quantum-well (MQW) active layer. Phase analysis 2θ-scan proved the composition of GaN (0002) and (0004) at 34.63oand 72.98o, respectively. Rocking curveφ-scan showed six significant peaks of the hexagonal GaN structures with consistent angular gaps of ~60o. From x-ray rocking curve (XRC)ω-scan, screw and mix dislocation density is found as 2.85 × 109cm-2, while pure edge dislocation density is found as 2.23 × 1011cm-2.

Sign in / Sign up

Export Citation Format

Share Document