Copper K-edge X-ray absorption studies of La{sub 2-x}K{sub x}CuO{sub 4} superconductors, Ba{sub 4}NaCuO{sub 4}(CO{sub 3}){sub 2}, and NdCu{sub 2}O{sub 4}
- Univ. of California, Berkeley, CA (United States)
- Du Pont Co., Wilmington, DE (United States)
X-ray near-edge absorption spectroscopy (XANES) measurements are reported at the Cu K-edge for La{sub 2-x}K{sub x}CuO{sub 4} superconductors with x = 0.1 and 0.2. Comparisons of the data were made with the absorption spectra of a Cu(II) standard (La{sub 2}CuO{sub 4}), a new Cu(III) standard (Ba{sub 4}NaCuO{sub 4}(CO{sub 3}){sub 2}), and a new mixed-valent Cu(II)/Cu(III) phase (NdCu{sub 2}O{sub 4}). There is a consistent increase in the energy of the main Cu absorption edge in the following series: La{sub 2}CuO{sub 4} < La{sub 1.9}K{sub 0.1}CuO{sub 4} < La{sub 1.8}K{sub 0.2}CuO{sub 4} {approximately} NdCu{sub 2}O{sub 4} < Ba{sub 4}NaCuO{sub 4}(CO{sub 3}){sub 2}. This trend can be attributed to an increase in the average Cu valence and to a decrease in bond length and an increase in covalency. The magnitude of the energy shift from Cu(II) to Cu(III) for the main absorption edge is {approximately}3 eV. There is no measurable change in the energy of the pre-edge feature irrespective of Cu valence. Furthermore, no new features appear at the edge for samples with formal oxidation state between 2 and 3, even for NdCu{sub 2}O{sub 4}, which contains both Cu(II) and Cu(III) in crystallographically distinct sites.
- OSTI ID:
- 518418
- Journal Information:
- Inorganic Chemistry, Vol. 36, Issue 9; Other Information: PBD: 23 Apr 1997
- Country of Publication:
- United States
- Language:
- English
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