Oxygen nonstoichiometry and valence of copper in the Cu-1222 superconductor

M. Karppinen; M. Arai; J. M. Lee; T. S. Chan; Y. Morita; J. M. Chen; R. S. Liu; H. Yamauchi

doi:10.1016/j.jssc.2005.03.026

Oxygen nonstoichiometry and valence of copper in the Cu-1222 superconductor

M. Karppinen^*, M. Arai, J. M. Lee, T. S. Chan, Y. Morita, J. M. Chen, R. S. Liu, H. Yamauchi

^*Corresponding author for this work

Research output: Contribution to journal › Article › Scientific › peer-review

4 Citations (Scopus)

Abstract

Essentially single-phase Cu(Ba_0.67Eu_0.33) ₂(Ce_0.33Eu_0.67)₂Cu₂O _9±δ samples of the Cu-1222 phase with a fluorite-structured (Ce,Eu)-O₂-(Ce,Eu) block between the superconductive CuO₂ planes were synthesized in O₂ atmosphere to exhibit superconductivity with T_c around 25 K. Wide-range tuning of oxygen content and thereby the overall hole-doping level of the phase was found possible through (i) temperature-controlled oxygen-depletion (TCOD) annealing carried out in a thermobalance in N ₂ at various temperatures (for reduction), and (ii) high-pressure oxygenation (HPO) treatments carried out in a cubic-anvil-type high-pressure apparatus in the presence of various amounts of Ag₂O₂ as an excess oxygen source (for oxidation). For the HPO samples a record-high T_c value of 62 K was achieved. On the other hand, deoxygenation to the oxygen content less than 9±δ≈8.9 was found to kill superconductivity. The degree of hole doping (both in overall and for the CuO₂ plane and CuO_1±δ charge reservoir separately) in the samples is discussed on the bases of Cu L-edge and O K-edge XANES data.

Original language	English
Pages (from-to)	1705-1711
Number of pages	7
Journal	Journal of Solid State Chemistry
Volume	178
Issue number	5
DOIs	https://doi.org/10.1016/j.jssc.2005.03.026
Publication status	Published - May 2005
MoE publication type	A1 Journal article-refereed

Keywords

Cu valence
XANES spectroscopy

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title = "Oxygen nonstoichiometry and valence of copper in the Cu-1222 superconductor",

abstract = "Essentially single-phase Cu(Ba0.67Eu0.33) 2(Ce0.33Eu0.67)2Cu2O 9±δ samples of the Cu-1222 phase with a fluorite-structured (Ce,Eu)-O2-(Ce,Eu) block between the superconductive CuO2 planes were synthesized in O2 atmosphere to exhibit superconductivity with Tc around 25 K. Wide-range tuning of oxygen content and thereby the overall hole-doping level of the phase was found possible through (i) temperature-controlled oxygen-depletion (TCOD) annealing carried out in a thermobalance in N 2 at various temperatures (for reduction), and (ii) high-pressure oxygenation (HPO) treatments carried out in a cubic-anvil-type high-pressure apparatus in the presence of various amounts of Ag2O2 as an excess oxygen source (for oxidation). For the HPO samples a record-high Tc value of 62 K was achieved. On the other hand, deoxygenation to the oxygen content less than 9±δ≈8.9 was found to kill superconductivity. The degree of hole doping (both in overall and for the CuO2 plane and CuO1±δ charge reservoir separately) in the samples is discussed on the bases of Cu L-edge and O K-edge XANES data.",

keywords = "Cu valence, XANES spectroscopy",

author = "M. Karppinen and M. Arai and Lee, {J. M.} and Chan, {T. S.} and Y. Morita and Chen, {J. M.} and Liu, {R. S.} and H. Yamauchi",

year = "2005",

month = may,

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language = "English",

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T1 - Oxygen nonstoichiometry and valence of copper in the Cu-1222 superconductor

AU - Karppinen, M.

AU - Arai, M.

AU - Lee, J. M.

AU - Chan, T. S.

AU - Morita, Y.

AU - Chen, J. M.

AU - Liu, R. S.

AU - Yamauchi, H.

PY - 2005/5

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N2 - Essentially single-phase Cu(Ba0.67Eu0.33) 2(Ce0.33Eu0.67)2Cu2O 9±δ samples of the Cu-1222 phase with a fluorite-structured (Ce,Eu)-O2-(Ce,Eu) block between the superconductive CuO2 planes were synthesized in O2 atmosphere to exhibit superconductivity with Tc around 25 K. Wide-range tuning of oxygen content and thereby the overall hole-doping level of the phase was found possible through (i) temperature-controlled oxygen-depletion (TCOD) annealing carried out in a thermobalance in N 2 at various temperatures (for reduction), and (ii) high-pressure oxygenation (HPO) treatments carried out in a cubic-anvil-type high-pressure apparatus in the presence of various amounts of Ag2O2 as an excess oxygen source (for oxidation). For the HPO samples a record-high Tc value of 62 K was achieved. On the other hand, deoxygenation to the oxygen content less than 9±δ≈8.9 was found to kill superconductivity. The degree of hole doping (both in overall and for the CuO2 plane and CuO1±δ charge reservoir separately) in the samples is discussed on the bases of Cu L-edge and O K-edge XANES data.

AB - Essentially single-phase Cu(Ba0.67Eu0.33) 2(Ce0.33Eu0.67)2Cu2O 9±δ samples of the Cu-1222 phase with a fluorite-structured (Ce,Eu)-O2-(Ce,Eu) block between the superconductive CuO2 planes were synthesized in O2 atmosphere to exhibit superconductivity with Tc around 25 K. Wide-range tuning of oxygen content and thereby the overall hole-doping level of the phase was found possible through (i) temperature-controlled oxygen-depletion (TCOD) annealing carried out in a thermobalance in N 2 at various temperatures (for reduction), and (ii) high-pressure oxygenation (HPO) treatments carried out in a cubic-anvil-type high-pressure apparatus in the presence of various amounts of Ag2O2 as an excess oxygen source (for oxidation). For the HPO samples a record-high Tc value of 62 K was achieved. On the other hand, deoxygenation to the oxygen content less than 9±δ≈8.9 was found to kill superconductivity. The degree of hole doping (both in overall and for the CuO2 plane and CuO1±δ charge reservoir separately) in the samples is discussed on the bases of Cu L-edge and O K-edge XANES data.

KW - Cu valence

KW - XANES spectroscopy

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ER -

Oxygen nonstoichiometry and valence of copper in the Cu-1222 superconductor

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