The structures of some titanium-niobium oxides by powder neutron diffraction

1974 ◽  
Vol 338 (1614) ◽  
pp. 311-326 ◽  
Keyword(s):  
Neutron Diffraction ◽  
Profile Analysis ◽  
Detailed Examination ◽  
Ionic Model ◽  
Space Group ◽  
Cell Parameters ◽  
Powder Neutron Diffraction ◽  
Crystallographic Shear ◽  
Final Profile ◽  
Block Structures

The structures of TiNb 2 O 7 and ortho - Ti 2 Nb 10 O 29 have been examined at 4.2 K by total profile analysis of powder neutron diffraction data. The space group of TiNb 2 O 7 is A2/m and the cell parameters are a = 11.890(5), b = 3.804(2), c = 20.373(9) Å, ‡ β = 120.199 (3) deg. The final profile residual was 9.47%. The space group of ortho-Ti 2 Nb 10 O 29 is Amma and the cell parameters are a = 28.305(12), b = 3.780(2), c = 20.352(9) Å. A final profile residual of 10.62% was obtained. Substantial ordering of the cations among the different metal sites in these block structures was found, with titanium occupancy numbers varying from 14.0 to 64.5% for TiNb 2 O 7 and from 4.5 to 40.0% in ortho-Ti 2 Nb 10 O 29 . The values are consistent with site potentials obtained on an ionic model. The oxygen positions were determined with greater precision than in previous studies of block structures, affording a detailed examination of the dis­tortions around the crystallographic shear planes.

Crystallographic Studies of Nd3-xYxFe27.5TM1.5(0.6≤x≤2.4, TM=Ti, Mo) Compounds

2013 ◽  
Vol 785-786 ◽  
pp. 634-637
Author(s):  
Song Bai Han ◽  
Yun Tao Liu
Keyword(s):  
Neutron Diffraction ◽  
Type Structure ◽  
Space Group ◽  
Powder Neutron Diffraction ◽  
Thermodynamic Effects

Nd3-xYxFe27.5Ti1.5(0.6≤x≤2.4) and Nd3-x’Yx’Fe27.5Mo1.5(0.6≤x’≤2.4) alloys have been synthesized successfully and studied by means of powder neutron diffraction. The structural analyses indicate that the main phases in all cases crystallize in the monoclinic Nd3(Fe,Ti)29-type structure with a space group A2/m. Ti and Mo prefer to occupy 4g, 4i1 and 4i2 sites exclusively and the elemental site occupancies are dominated by the site sizes and thermodynamic effects.

Crystallographic studies of BaR2ZnO5 (R=La, Nd, Dy, Ho, Er, and Y)

1998 ◽  
Vol 13 (3) ◽  
pp. 144-151 ◽  
Author(s):  
Winnie Wong-Ng ◽  
Brian Toby ◽  
William Greenwood
Keyword(s):  
Neutron Diffraction ◽  
Crystal Structures ◽  
Lattice Parameters ◽  
Trigonal Prism ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters

The crystal structures of BaR2ZnO5, where R=La, Nd, Dy, Ho, and Y, were studied by neutron diffraction, and that of the Er analog was investigated by synchrotron X-ray diffraction. Two structure types were confirmed for this series of compounds and agreed with those reported in literature. The compounds with a smaller size of R (R=Dy, Ho, Y, and Er) are isostructural to the orthorhombic “green phase (BaY2CuO5)” compounds. The cell parameters for compounds with the R=Er to Dy range from a=7.0472(1) Å to 7.0944(1) Å, b=12.3022(1) Å to 12.3885(2) Å, and c=5.6958(1) Å to 5.7314(1) Å, respectively. R is 7-fold coordinated inside a monocapped trigonal prism. These prisms share edges to form wavelike chains parallel to the long b-axis. The Ba atoms reside in 11-fold coordinated cages. The compounds which contain a larger size R (R=La and Nd) crystallize in the tetragonal I4/mcm space group, but are not isostructural to the “brown phases” BaR2CuO5. The lattice parameters for the La and Nd analogs are a=6.9118(1) Å, c=11.6002(2) Å for BaLa2ZnO5, and a=6.7608(1) Å and c=11.5442(2) Å for BaLa2ZnO5. The structure consists of ZnO4 tetrahedral groups (instead of planar CuO4 groups as found in the brown phase) with Ba ions inserted in between. The structure can be viewed as consisting of alternate layers of Zn-Ba-O and Nd-O extending infinitely in the xy plane and perpendicular to the z-axis.

Crystal and powder neutron diffraction data of Tl3Li(MO4)2 (M=Mo, W)

1998 ◽  
Vol 13 (4) ◽  
pp. 244-245
Author(s):  
A. M. Xuriguera ◽  
C. Colbeau Justin ◽  
A. Elfakir ◽  
M. Quarton
Keyword(s):  
Solid State ◽  
Neutron Diffraction ◽  
Diffraction Data ◽  
Neutron Diffraction Data ◽  
Powder Diffraction Data ◽  
Unit Cell Parameters ◽  
Cell Parameters ◽  
Powder Neutron Diffraction ◽  
Related Compounds ◽  
Powder Neutron Diffraction Data

Two structurally related compounds, Tl3Li(MoO4)2 and Tl3Li(WO4)2, have been synthesized by solid state reaction. Space group (P63mc) and unit-cell parameters [a(Å)=6.00392(3); c(Å)=15.8203(1) and a(Å)=6.03484(3); c(Å)=15.81759(9), respectively, for Tl3Li(MoO4)2 and Tl3Li(WO4)2] were determined. Powder diffraction data for each phase are reported.

A NEUTRON DIFFRACTION STUDY OF A SUPERCONDUCTING CUPRATE OF THE Bi–Ca–Sr–Cu–O SYSTEM CONTAINING TWO Cu-O SHEETS

1989 ◽  
Vol 03 (03) ◽  
pp. 445-454 ◽  
Author(s):  
A. SEQUEIRA ◽  
H. RAJAGOPAL ◽  
L. GANAPATHI ◽  
R. VIJAYARAGHAVAN ◽  
C. N. R. RAO
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Study ◽  
Profile Analysis ◽  
Neutron Diffraction Study ◽  
Diffraction Profile ◽  
Space Group

The structure of a nominally Ca-rich composition of the n = 2 member of the Bi 2 (Ca, Sr) n+1 Cu n O 2n+4 series has been investigated by neutron diffraction profile analysis. The results suggest that the Amaa space group may be more appropriate than the Fmmm space group.

The structure of Na2UCl6 and Li2UCl6 from multiphase powder neutron profile refinement

1983 ◽  
Vol 16 (2) ◽  
pp. 164-170 ◽  
Author(s):  
P. J. Bendall ◽  
A. N. Fitch ◽  
B. E. F. Fender
Keyword(s):  
Neutron Diffraction ◽  
Room Temperature ◽  
Lithium Ions ◽  
Two Phase ◽  
Relative Ease ◽  
Space Group ◽  
Octahedral Sites ◽  
Powder Neutron Diffraction ◽  
Phase Mixture ◽  
Profile Refinement

The structures of Na2UCl6 and Li2UCl6 have been determined by powder neutron diffraction at room temperature in the presence of NaCl and LiCl respectively as impurity. Na2UCl6crystallizes in space group P{\bar 3}m1, with a = 11 8062(9), c = 6.3243(2) Å, and Z = 3. The best description of Li2UCl6 was found in space group P63/mmc, a = 11.1915(5), c = 6.0356(1) Å, and Z = 3, with uranium and lithium ions disordered over the available octahedral sites. The results give the first illustration of the relative ease of analysing a two-phase mixture using a Rietveld profile program adapted to refine simultaneously more than one phase.

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