Hole doping into Co-12s2 copper oxides with s fluorite-structured layers between CuO2 planespiezolaminated composite plate
Resource
Journal of Solid State Chemistry (179),632–645
Journal
Journal of Solid State Chemistry (179),632–645
Pages
-
Date Issued
2006
Date
2006
Author(s)
Fjellvag, H.
Moritaa, Y.
Nagai, T.
Lee, J.M.
Chen, J.M.
Liu, R.S.
Hauback, B.C.
Awana, V.P.S.
Matsui, Y.
Yamauchi, H.
Karppinen, M.
DOI
246246/2006111501275479
Abstract
In this work, the first three members (s ¼ 1, 2, 3) of the Co-12s2 homologous series of multi-layered copper oxides are gradually doped
with holes through high-pressure oxygenation (HPO). The phases differ from each other only by thickness of the fluorite-structured layer
block, (Ce,Y,Ca)–[O2–(Ce,Y)]s1, between two identical CuO2 planes. High-resolution transmission-electron microscopy (HRTEM) and
electron diffraction (ED) analyses together with both synchrotron X-ray and neutron powder diffraction data, reveal that as a
consequence of HPO the charge-reservoir CoO4-tetrahedra chains get broken and the lattice symmetry of the Co-12s2 phases changes
from orthorhombic to tetragonal. Oxygen contents are analyzed for the samples with wet-chemical and thermogravimetric techniques.
The valence state of copper in the CuO2 plane is determined from Cu L-edge X-ray absorption near-edge structure (XANES) spectra to
be compared with the values estimated through bond-valence-sum (BVS) calculations from the crystal structure data. The positive charge
induced by oxygen loading (or aliovalent CaII-for-YIII substitution in CoSr2YCu2O7+d) is found not to be completely accommodated in
the CuO2 planes but be rather effectively trapped at the charge-reservoir Co atoms. Superconductivity appears in the Co-1212
(CoSr2YCu2O7+d) samples with the copper valence of 2.13 or higher, whereas in the Co-1222 (CoSr2(Ce0.25Y0.75)2Cu2O9+d) and Co-
1232 (CoSr2(Ce0.67Y0.33)3Cu2O11+d) samples Cu valence does not increase high enough to induce superconductivity.
Subjects
Multi-layered copper oxides
Fluorite-structured layers
Co-12s2 homologous series
Crystal structure
Oxygen content
Hole-doping
Cu valence
XANES spectroscopy
Superconductivity
Publisher
Taipei:National Taiwan University Dept Mech Engn
Type
journal article
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