Effect of aluminum titanate additives on crystal structure parameters and sintering of zirconia dioxide

2020 ◽  
pp. 29-34
Author(s):  
M. I. Tenevich ◽  
A. P. Shevchik ◽  
V. N. Fischev
Keyword(s):  
Crystal Structure ◽  
Structure Parameters ◽  
Aluminum Titanate

Structure of Carbonated Hydroxyapatite Based on Rietveld Method

2008 ◽  
Vol 368-372 ◽  
pp. 1187-1189
Author(s):  
Xu Ran ◽  
Jun Guo Ran ◽  
Li Gou ◽  
Ji Yong Chen ◽  
Jiao Min Luo
Keyword(s):  
Crystal Structure ◽  
Sintering Temperature ◽  
Rietveld Method ◽  
Rietveld Analysis ◽  
Structure Parameters ◽  
X Ray Diffraction ◽  
Carbonated Hydroxyapatite ◽  
X Ray ◽  
Quantitative Results ◽  
Distortion Index

The crystalline structures of B-type carbonated hydroxyapatite (CHA) powders sintered at 700, 900 and 1100°C, respectively, were studied by Rietveld analysis of powder X-ray diffraction (XRD) data. A series of structure parameters, including lattice parameters (a and c), bond length and the distortion index of PO4 tetrahedron (Dind) were calculated by Rietveld method to characterize the fine structure of CHA. The broadening effect of XRD reflections was separated to calculate the micro-strain and crystalline size. The results showed that CHA become more stable with the increase of sintering temperature, but the CO3 2- is almost lost at temperature of 1100°C. The quantitative results about crystal structure of CHA based on crystalline structure simulated by Rietveld method are obtained.

Real-space technique applied to crystal structure determination from powder data

2002 ◽  
Vol 35 (2) ◽  
pp. 182-184 ◽  
Author(s):  
Angela Altomare ◽  
Corrado Cuocci ◽  
Carmelo Giacovazzo ◽  
Antonietta Guagliardi ◽  
Anna Grazia Giuseppina Moliterni ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Structural Model ◽  
Real Space ◽  
Structure Parameters ◽  
Powder Diffraction Data ◽  
Structure Solution ◽  
Phase Extension ◽  
Space Technique ◽  
New Process

Real-space techniques used for phase extension and refinement in the modern direct procedures forab initiocrystal structure solution of proteins have been optimized for application to powder diffraction data. The new process has been implemented in a modified version ofEXPO[Altomareet al.(1999).J.Appl.Cryst.32, 339–340]. The method is able to supply a structural model that is more complete than that provided by the standardEXPOprogram. The model is then refinedviaa diagonal least-squares procedure, but only when the ratio of the number of observations to the number of structure parameters to be refined is larger than a given threshold.

Phase diagram of the Nd2Fe14B–Sm2Fe14B pseudo-binary system

2016 ◽  
Vol 49 (1) ◽  
pp. 64-68 ◽  
Author(s):  
Ch. F. Xu ◽  
K. H. Chen ◽  
Z. F. Gu ◽  
L. Y. Cheng ◽  
D. D. Ma ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Diagram ◽  
Binary System ◽  
Solid Solutions ◽  
Structure Parameters ◽  
Rietveld Refinements ◽  
X Ray ◽  
Full Profile ◽  
Cell Volumes ◽  
Scanning Electron

The phase relations in the (1−x)Nd2Fe14B–xSm2Fe14B system over the whole concentration range have been studied by means of X-ray powder diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy with energy-dispersive X-ray spectroscopy. Crystal structure parameters for all studied compositions of (Nd1−xSmx)2Fe14B have been determined by full-profile Rietveld refinements. These results revealed that all intermediate alloys of (Nd1−xSmx)2Fe14B are similar to the end member of the investigated system, Nd2Fe14B, with a tetragonal structure (space groupP42/mnm). The formation of continuous solid solutions has been found in this system. The normalized lattice parameters and unit-cell volumes of (Nd1−xSmx)2Fe14B solid solutions decrease linearly with increasing Sm content. The DTA measurements show that the melting temperature of (Nd1−xSmx)2Fe14B increases linearly with increasing Sm content and no metastable phases were detected. Based on the DTA data and XRD results, a tentative phase diagram for the pseudo-binary system Nd2Fe14B–Sm2Fe14B has been constructed.

Is there an N3− ion in the crystal structure of the ionic conductor lithium nitride (Li3N)?

1978 ◽  
Vol 34 (6) ◽  
pp. 999-1005 ◽  
Author(s):  
H. Schulz ◽  
K. Schwarz
Keyword(s):  
Crystal Structure ◽  
Ionic Crystal ◽  
Ionic Conductor ◽  
Small Range ◽  
Structure Parameters ◽  
Neutral Atoms ◽  
Lithium Nitride ◽  
Temperature Range ◽  
Free Ion

The structure parameters of Li3N in the temperature range -120 to 20°C were refined both for neutral atoms (Li0 and N0) and for ions (Li+ and N3-). For N3- new scattering curves were used which were calculated by applying stabilizing Watson-sphere potentials for different radii. All structure parameters depend critically on the scattering curves used. However, only on the assumption of ions, and only for N3- scattering curves corresponding to a small range of Watson radii, were physically meaningful structure parameters and R values down to 0.9% obtained. These structure refinements demonstrate that Li3N can be considered as an ionic crystal in which the N3- ion, though unstable as a free ion, is stabilized by the surrounding Li+ ions.

Sign in / Sign up

Export Citation Format

Share Document