skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Synthesis and Neutron Powder Diffraction Structural Analysis of Oxidized Delafossite YCuO 2.5

Abstract

We report a study of the evolution of the structure of the delafossite-derived compounds YCuO{sub 2+{delta}} as a function of oxygen stoichiometry. The structural details of the oxygenated material YCuO{sub 2.5} were examined by means of high-resolution neutron powder diffraction. We confirmed that YCuO{sub 2.5} adopts an orthorhombic superstructure (a = {radical}3a{sub H}, b=c{sub H}, c=2a{sub H}) in which the anions are located at the center of corner-sharing triangles to form undulating chains of Cu{sup 2+} (s=1/2), running along a-axis direction.

Authors:
 [1];  [2];  [2];  [2]
  1. ORNL
  2. Laboratoire of Cristallographie, Grenoble
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); High Flux Isotope Reactor
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931928
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Solid State Sciences; Journal Volume: 8
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ANIONS; CHAINS; DIFFRACTION; NEUTRONS; OXYGEN; STOICHIOMETRY; SYNTHESIS

Citation Formats

Garlea, Vasile O, Darie, Celine, Isnard, Olivier, and Bordet, Pierre. Synthesis and Neutron Powder Diffraction Structural Analysis of Oxidized Delafossite YCuO2.5. United States: N. p., 2006. Web. doi:10.1016/j.solidstatesciences.2005.12.003.
Garlea, Vasile O, Darie, Celine, Isnard, Olivier, & Bordet, Pierre. Synthesis and Neutron Powder Diffraction Structural Analysis of Oxidized Delafossite YCuO2.5. United States. doi:10.1016/j.solidstatesciences.2005.12.003.
Garlea, Vasile O, Darie, Celine, Isnard, Olivier, and Bordet, Pierre. Sun . "Synthesis and Neutron Powder Diffraction Structural Analysis of Oxidized Delafossite YCuO2.5". United States. doi:10.1016/j.solidstatesciences.2005.12.003.
@article{osti_931928,
title = {Synthesis and Neutron Powder Diffraction Structural Analysis of Oxidized Delafossite YCuO2.5},
author = {Garlea, Vasile O and Darie, Celine and Isnard, Olivier and Bordet, Pierre},
abstractNote = {We report a study of the evolution of the structure of the delafossite-derived compounds YCuO{sub 2+{delta}} as a function of oxygen stoichiometry. The structural details of the oxygenated material YCuO{sub 2.5} were examined by means of high-resolution neutron powder diffraction. We confirmed that YCuO{sub 2.5} adopts an orthorhombic superstructure (a = {radical}3a{sub H}, b=c{sub H}, c=2a{sub H}) in which the anions are located at the center of corner-sharing triangles to form undulating chains of Cu{sup 2+} (s=1/2), running along a-axis direction.},
doi = {10.1016/j.solidstatesciences.2005.12.003},
journal = {Solid State Sciences},
number = ,
volume = 8,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • The crystal and molecular structure of the unusual complex Tl/sub 4/(Pt(CN)/sub 4/)CO/sub 3/, obtained by mixing Tl/sub 2/(Pt(CN)/sub 4/) and Tl/sub 2/CO/sub 3/ in aqueous solution at 95/sup 0/C, was determined by both single-crystal and time-of-flight powder neutron diffraction. The complex is not a partially oxidized tetracyanoplatinate (POTCP) salt and contains Pt in an integral (2.0) oxidation state. The lustrous metallic green complex crystallizes in the tetragonal space group, with unit cell constants a = b = 9.911 (4) A (9.908 (3) A, powder study), c = 6.490 (3) A (6.487 (2) A), and V/sub c/ = 637.5 A/sup 3/more » at 298/sup 0/K. In the single-crystal study diffracted intensities of 267 independent reflections were measured to a (sin theta)/lambda limit of 0.438 A/sup -1/, and of these 202 had F/sub 0//sup 2/ > sigma(F/sub 0//sup 2/). Full-matrix least-squares refinement of all structural parameters resulted in a final R(F/sub 0//sup 2/) = 0.075 (all data) and R(F/sub 0//sup 2/) = 0.068. It is important to note that the structural parameters derived with use of the time-of-flight neutron diffraction and single-crystal methods are, in this case, virtually identical. The most pertinent structural feature in Tl/sub 4/(Pt(CN)/sub 4/)CO/sub 3/ is that the Pt atoms form perfectly linear chains with Pt-Pt separations crystallographically constrained to a value of (c/2) = 3.245 (3) A. The intrachain Pt-Pt separation is much longer than in the partially oxidized salts (2.80 to 2.96 A) and accounts for the low electrical conductivity in this salt. The structure is composed of square-planar Pt(CN)/sub 4//sup 2 -/ groups linked by Tl/sup +/ cations, all of whichoccupy the same molecular plane, and carbonate groups which lie between the Pt(CN)/sub 4//sup 2 -/ groups. The CO/sub 3//sup 2 -/ group oxygen atoms are clearly disordered among at least two positions, creating six partially occupied oxygen atom sites per group. The Tl/sup +/ and O separations are approx. 0.2 A shorter than the sum of the ionic radii which is probably an artifact of disorder.« less
  • A new material of nominal stoichiometry YGaMnO{sub 5} has been prepared in polycrystalline form from citrate precursors followed by thermal treatments under high-oxygen pressure. This compound has been characterized from neutron powder diffraction (NPD) data and magnetic measurements. For comparison, the parent compound YMn{sub 2}O{sub 5} has also been synthesized and its crystal structure refined by NPD data. The new oxide has an actual stoichiometry YGa{sub 1-x}Mn{sub 1+x}O{sub 5} (x = 0.23), determined by NPD, showing an important cationic disorder between both metal sites; it is orthorhombic, Pbam (SG), and its crystal structure contains chains of Mn{sup 4+}O{sub 6} edge-sharingmore » octahedra, linked together by Ga{sup 3+}O{sub 5} pyramids and YO{sub 8} units. With respect to YMn{sub 2}O{sub 5}, containing axially elongated MnO{sub 5} pyramids due to the Jahn-Teller effect of Mn{sup 3+} cations, the GaO{sub 5} pyramidal units in YGa{sub 0.77}Mn{sub 1.23}O{sub 5} are substantially flattened. This compound has a paramagnetic behaviour with two weak anomalies at about 50 K and 350 K. The magnetic structures, studied at 1.4 K and 100 K show a ferromagnetic coupling along the chains of MnO{sub 6} octahedra.« less
  • From neutron diffraction data collected at 3 K on a powder of La{sub 9.67}(SiO{sub 4}){sub 6}O{sub 2.5} composition and a careful examination of the average structure, a model was proposed to explain the oxygen over-stoichiometry in the apatite structure. This model leads to realistic distances to neighbouring atoms. Moreover, it accounts perfectly for the maximum oxygen content observed in these materials. Up to 0.5 oxygen atom located at the vicinity of the 2a site (0, 0, 1/4) would be shifted to a new interstitial position in the channel at (-0.01, 0.04, 0.06), creating a Frenkel defect, with the possibility ofmore » a maximum occupancy in this site equal to twice the Frenkel defect numbers. This structural model is in good agreement with the oxygen diffusion pathways recently proposed by Bechade et al. (2009) using computer modeling techniques. It supports preferred oxygen diffusion pathways via interstitial oxygen atoms and vacant sites along [0 0 1], close to the centre of the La(2)-O channels. - Graphical abstract legend: Structural defect position and possible conduction mechanism along the c-axis (representation of two adjacent unit-cells)« less
  • The main structural findings reported here, which bear on the diminished electrical conductivity of (NH/sub 4/)/sub 2/(Pt(CN)/sub 4/)Cl/sub 0/./sub 3/ . 3H/sub 2/O compared to prototype K/sup 2/(Pt(CN)/sub 4/)Br/sub 0/./sub 3/ . 3H/sub 2/O, are that while the intrachain Pt-Pt spacings are shorter and are of equal length (2.88(1)A) in the K+ salt, they are longer and are of different length (2.910(5) and 2.930(5)A x rays) in the NH/sub 4//sup +/ salt. Thus the formation of alternately long and short Pt-Pt separations (dimerization) in NH/sub 4/CP(Cl) is likely one of the most important factors contributing to its electrical conduction properties.more » A factor which supports hypothesis is that in RbCP(Cl), the Pt-Pt distances are also of unequal length (2.924(8) and 2.877(8)A), and Rb CP(Cl) has lower room temperature conductivity than KCP(Br). The complete explanation for the structure-conductivity relationships in those POTCP complexes is obviously much more complicated, because although a Rb/sup +/ ion has nearly the same cation radius as NH/sub 4//sup +/ and RbCP(Cl) and NH/sub 4/CP(Cl) are isostructural, the low-temperature electrical conductivity (NH/sub 4/CP(Cl)<< RbCP(Cl)) is vastly different.« less