Probing Octahedral Tilting in Dion-Jacobson Layered Perovskites With Neutron Powder Diffraction and Raman Spectroscopy

2006 ◽  
Vol 988 ◽  
Author(s):  
Joshu A. Kurzman ◽  
Margret J. Geselbracht
Keyword(s):  
Raman Spectroscopy ◽  
Powder Diffraction ◽  
Neutron Powder Diffraction ◽  
Layered Perovskite ◽  
Strontium Content ◽  
Solid Solution Formation ◽  
X Ray ◽  
Unit Cells ◽  
Octahedral Tilting ◽  
Average Size

AbstractTwo new Dion-Jacobson type layered perovskite solid solutions, RbCa2-xSrxM3O10 (M = Nb, Ta; 0 ≤ x ≤ 2), were prepared and studied by X-ray powder diffraction, neutron powder diffraction, and Raman spectroscopy. X-ray powder diffraction confirmed single-phase solid solution formation with continuous expansion of the idealized primitive tetragonal unit cell with increasing strontium content. Neutron powder diffraction studies of selected samples revealed lower symmetries and larger unit cells, as necessitated by octahedral tilting within the perovskite slabs, compared to the idealized primitive cell. As the average size of the A-cation in the perovskite slab is varied from Sr2+ to Ca2+, more extensive octahedral tilting is introduced. Vibrational modes of the perovskite slab observed using Raman spectroscopy show subtle changes as a function of calcium/strontium content and more intriguing differences between the isostructural niobates and tantalates.

scholarly journals Synthesis and Structure of Oxygen Deficient Lead-Technetium Pyrochlore, the First Example of a Valence V Technetium Oxide

2021 ◽  
Vol 9 ◽  
Author(s):  
Brendan J. Kennedy ◽  
Timothy A. Ablott ◽  
Maxim Avdeev ◽  
Melody L. Carter ◽  
Linda Losurdo ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Electron Diffraction ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Neutron Powder Diffraction ◽  
Oxygen Stoichiometry ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Neutron Powder Diffraction Data ◽  
X Ray Absorption

The structure of lead-technetium pyrochlore has been refined in space group Fd3¯m with a = 10.36584(2) Å using a combination of synchrotron X-ray and neutron powder diffraction data and confirmed via Electron Diffraction. The oxide is found to be oxygen deficient with a stoichiometry of Pb2Tc2O7-d. Displacive disorder of the Pb cations is evident from the refinements, as has been observed in Bi2Tc2O7-d. X-ray absorption spectroscopic measurements at the Tc K-edge demonstrate the valence of the Tc is greater than 4.0 as anticipated from the refined oxygen stoichiometry. Raman spectroscopy confirms the presence of disorder leading us to conclude that this pyrochlore is the first example of a valence V technetium oxide.

The crystal structure of the B-site ordered complex perovskite Sr(Yb0.5Nb0.5)O3

1999 ◽  
Vol 55 (3) ◽  
pp. 348-354 ◽  
Author(s):  
Jae Ho Yang ◽  
Woong Kil Choo ◽  
Jin Ho Lee ◽  
Chang Hee Lee
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Room Temperature ◽  
Neutron Powder Diffraction ◽  
Rigid Rotation ◽  
Complex Perovskite ◽  
X Ray ◽  
Transmission Electron ◽  
Octahedral Tilting ◽  
Volume Difference

The room-temperature crystal structure of the B-site ordered complex perovskite strontium ytterbium niobate, Sr(Yb0.5Nb0.5)O3 [monoclinic, Z = 2, P21/n (set 2), a = 5.79095 (8), b = 5.82210 (7), c = 8.20358 (12) Å, β = 90.126 (1)°, with final R wp = 0.0595, R Bragg = 0.0203 for the neutron profile and R wp = 0.0832, R Bragg = 0.0193 for the X-ray profile, respectively], was determined by X-ray powder diffraction, high-resolution neutron powder diffraction and transmission electron microscopy. This compound shows a slight triclinic distortion from the prototype doubled cubic perovskite cell as a result of an a − a − c +-type oxygen octahedral tilting distortion. It is also shown that the site ordering of the different species of B-site cations, Yb3+ and Nb5+, inherently leads to a difference between the volumes of the YbO6 and NbO6 octahedra. This volume difference is shown to inevitably inhibit the rigid rotation of octahedra.

Powder X-Ray Diffraction Data for Ca2Bi2O5and C4Bi6O13

1992 ◽  
Vol 7 (2) ◽  
pp. 109-111 ◽  
Author(s):  
C.J. Rawn ◽  
R.S. Roth ◽  
H.F. McMurdie
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Neutron Powder Diffraction ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Cell Dimensions ◽  
Powder Samples ◽  
Orthorhombic Cell ◽  
Unit Cell Dimensions

AbstractSingle crystals and powder samples of Ca2Bi5O5and Ca4Bi6O13have been synthesized and studied using single crystal X-ray diffraction as well as X-ray and neutron powder diffraction. Unit cell dimensions were calculated using a least squares analysis that refined to a δ2θof no more than 0.03°. A triclinic cell was found with space group , a = 10.1222(7), b = 10.1466(6), c = 10.4833(7) Å. α= 116.912(5), β= 107.135(6) and γ= 92.939(6)°, Z = 6 for the Ca2Bi2O5compound. An orthorhombic cell was found with space group C2mm, a = 17.3795(5), b = 5.9419(2) and c = 7.2306(2) Å, Z = 2 for the Ca4Bi6O13compound.

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