Crystal growth, structure, and stoichiometry of the superconducting pyrochlore Cd 2Re 2O 7

J. He; R. Jin; B. C. Chakoumakos; J. S. Gardner; D. Mandrus; Terry M. Tritt

doi:10.1007/s11664-007-0087-7

Crystal growth, structure, and stoichiometry of the superconducting pyrochlore Cd ₂Re ₂O ₇

J. He, R. Jin, B. C. Chakoumakos, J. S. Gardner, D. Mandrus, Terry M. Tritt

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

10 Scopus citations

Abstract

We report single-crystal growth of the superconducting pyrochlore Cd ₂Re ₂O ₇ using a vapor transport technique. Several parameters of the growth conditions, including hot-zone temperature and starting stoichiometry, were varied in order to control the formation of ReO ₂ inclusions, as confirmed by the electron microscopy, resistivity, and magnetic susceptibility measurements. The Rietveld refinement of x-ray (neutron) powder diffraction was found to be consistent with a cubic structure Fd3m with lattice constant a = 10.2250 (10.2358) Å and reduced coordinate of O1 = 0.3184 (0.3177) at 293 K (250 K). We also studied the oxygen stoichiometry by means of redox reactions, electron microprobe analysis (EMPA), and x-ray/neutron diffractions. Particularly, the neutron powder diffraction on the ¹¹⁴Cd-enriched specimens yielded an oxygen deficiency δ = 0.14 ± 0.03 solely at the O2 site, which was consistent with the EMPA results. The EMPA indicated that the oxygen deficiency is homogeneous in the bulk and in a range of 0.01 ± 0.18-0.23 ± 0.19.

Original language	English
Pages (from-to)	740-745
Number of pages	6
Journal	Journal of Electronic Materials
Volume	36
Issue number	7
DOIs	https://doi.org/10.1007/s11664-007-0087-7
State	Published - Jul 2007

Funding

The authors thank C.J. Rawn (ORNL) and J. Bai (NSLS/ORNL) for their help on synchrotron x-ray diffraction measurement; C. Wilson and M. Gutt-man (ISIS) for their help on neutron scattering measurement; G. Ownby, A. Baddorf, and L. Walker (ORNL) for the X-ray Photoelectron Spectroscopy and EMPA measurements; and P. Kahlifar (ORNL) for the helpful discussion on chemistry of rhenium.The work at UT and ORNL is supported by NSF Grant No. DMR 007 2998. Oak Ridge National Laboratory is managed by UT–Battelle, LLC, for the U.S. Department of Energy, under Contract No. DE-AC05-00OR22725. Research carried out, in part, at the National Synchrotron Light Source, Brookhaven National Laboratory, is supported by the U.S. Department of Energy, Division of Materials Sciences and Division of Chemical Sciences.

Funders	Funder number
Division of Chemical Sciences
NSLS/ORNL
National Science Foundation
U.S. Department of Energy
Battelle
Oak Ridge National Laboratory
Division of Materials Sciences and Engineering

Keywords

Crystal structure
Inclusion
Oxygen deficiency
Stoichiometry

Access to Document

10.1007/s11664-007-0087-7

Cite this

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title = "Crystal growth, structure, and stoichiometry of the superconducting pyrochlore Cd 2Re 2O 7 ",

abstract = "We report single-crystal growth of the superconducting pyrochlore Cd 2Re 2O 7 using a vapor transport technique. Several parameters of the growth conditions, including hot-zone temperature and starting stoichiometry, were varied in order to control the formation of ReO 2 inclusions, as confirmed by the electron microscopy, resistivity, and magnetic susceptibility measurements. The Rietveld refinement of x-ray (neutron) powder diffraction was found to be consistent with a cubic structure Fd3m with lattice constant a = 10.2250 (10.2358) {\AA} and reduced coordinate of O1 = 0.3184 (0.3177) at 293 K (250 K). We also studied the oxygen stoichiometry by means of redox reactions, electron microprobe analysis (EMPA), and x-ray/neutron diffractions. Particularly, the neutron powder diffraction on the 114Cd-enriched specimens yielded an oxygen deficiency δ = 0.14 ± 0.03 solely at the O2 site, which was consistent with the EMPA results. The EMPA indicated that the oxygen deficiency is homogeneous in the bulk and in a range of 0.01 ± 0.18-0.23 ± 0.19.",

keywords = "Crystal structure, Inclusion, Oxygen deficiency, Stoichiometry",

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AU - Jin, R.

AU - Chakoumakos, B. C.

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AU - Mandrus, D.

AU - Tritt, Terry M.

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N2 - We report single-crystal growth of the superconducting pyrochlore Cd 2Re 2O 7 using a vapor transport technique. Several parameters of the growth conditions, including hot-zone temperature and starting stoichiometry, were varied in order to control the formation of ReO 2 inclusions, as confirmed by the electron microscopy, resistivity, and magnetic susceptibility measurements. The Rietveld refinement of x-ray (neutron) powder diffraction was found to be consistent with a cubic structure Fd3m with lattice constant a = 10.2250 (10.2358) Å and reduced coordinate of O1 = 0.3184 (0.3177) at 293 K (250 K). We also studied the oxygen stoichiometry by means of redox reactions, electron microprobe analysis (EMPA), and x-ray/neutron diffractions. Particularly, the neutron powder diffraction on the 114Cd-enriched specimens yielded an oxygen deficiency δ = 0.14 ± 0.03 solely at the O2 site, which was consistent with the EMPA results. The EMPA indicated that the oxygen deficiency is homogeneous in the bulk and in a range of 0.01 ± 0.18-0.23 ± 0.19.

AB - We report single-crystal growth of the superconducting pyrochlore Cd 2Re 2O 7 using a vapor transport technique. Several parameters of the growth conditions, including hot-zone temperature and starting stoichiometry, were varied in order to control the formation of ReO 2 inclusions, as confirmed by the electron microscopy, resistivity, and magnetic susceptibility measurements. The Rietveld refinement of x-ray (neutron) powder diffraction was found to be consistent with a cubic structure Fd3m with lattice constant a = 10.2250 (10.2358) Å and reduced coordinate of O1 = 0.3184 (0.3177) at 293 K (250 K). We also studied the oxygen stoichiometry by means of redox reactions, electron microprobe analysis (EMPA), and x-ray/neutron diffractions. Particularly, the neutron powder diffraction on the 114Cd-enriched specimens yielded an oxygen deficiency δ = 0.14 ± 0.03 solely at the O2 site, which was consistent with the EMPA results. The EMPA indicated that the oxygen deficiency is homogeneous in the bulk and in a range of 0.01 ± 0.18-0.23 ± 0.19.

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KW - Stoichiometry

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