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

Title: Crystal growth, structure, and stoichiometry of the superconducting pyrochlore Cd2Re2O7.

Abstract

We report single-crystal growth of the superconducting pyrochlore Cd2Re2O7 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 ReO2 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) A # 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 d = 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.

Authors:
 [1];  [2];  [2];  [3];  [2];  [1]
  1. Clemson University
  2. ORNL
  3. Brookhaven National Laboratory (BNL)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
958830
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Electronic Materials; Journal Volume: 36; Journal Issue: 7
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; CRYSTAL GROWTH; DIFFRACTION; ELECTRON MICROPROBE ANALYSIS; ELECTRON MICROSCOPY; MAGNETIC SUSCEPTIBILITY; NEUTRONS; OXYGEN; PYROCHLORE; REDOX REACTIONS; STOICHIOMETRY; TRANSPORT; Cd2Re2O7; pyrochlore; superconductor; neutron diffraction

Citation Formats

He, Jian, Jin, Rongying, Chakoumakos, Bryan C, Gardner, J. S., Mandrus, David, and Tritt, Terry M.. Crystal growth, structure, and stoichiometry of the superconducting pyrochlore Cd2Re2O7.. United States: N. p., 2007. Web. doi:10.1007/s11664-007-0087-7.
He, Jian, Jin, Rongying, Chakoumakos, Bryan C, Gardner, J. S., Mandrus, David, & Tritt, Terry M.. Crystal growth, structure, and stoichiometry of the superconducting pyrochlore Cd2Re2O7.. United States. doi:10.1007/s11664-007-0087-7.
He, Jian, Jin, Rongying, Chakoumakos, Bryan C, Gardner, J. S., Mandrus, David, and Tritt, Terry M.. Mon . "Crystal growth, structure, and stoichiometry of the superconducting pyrochlore Cd2Re2O7.". United States. doi:10.1007/s11664-007-0087-7.
@article{osti_958830,
title = {Crystal growth, structure, and stoichiometry of the superconducting pyrochlore Cd2Re2O7.},
author = {He, Jian and Jin, Rongying and Chakoumakos, Bryan C and Gardner, J. S. and Mandrus, David and Tritt, Terry M.},
abstractNote = {We report single-crystal growth of the superconducting pyrochlore Cd2Re2O7 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 ReO2 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) A # 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 d = 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.},
doi = {10.1007/s11664-007-0087-7},
journal = {Journal of Electronic Materials},
number = 7,
volume = 36,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • We report single-crystal growth of the superconducting pyrochlore Cd{sub 2}Re{sub 2}O{sub 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{sub 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) {angstrom} and reduced coordinate of O1 = 0.3184 (0.3177) at 293 K (250 K). We also studied the oxygen stoichiometry by means ofmore » redox reactions, electron microprobe analysis (EMPA), and x-ray/neutron diffractions. Particularly, the neutron powder diffraction on the {sup 114}Cd-enriched specimens yielded an oxygen deficiency {delta} = 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.« less
  • We report single-crystal growth of the superconducting pyrochlore Cd{sub 2}Re{sub 2}O{sub 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{sub 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) Angstroms and reduced coordinate of O1 = 0.3184 (0.3177) at 293 K (250 K). We also studied the oxygen stoichiometry by means ofmore » redox reactions, electron microprobe analysis (EMPA), and x-ray/neutron diffractions. Particularly, the neutron powder diffraction on the {sup 114}Cd-enriched specimens yielded an oxygen deficiency {delta} = 0.14 {+-} 0.03 solely at the O{sub 2} 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.« less
  • To investigate the crystallographic structure and the magnetic properties as a function of chemical composition (40–62 at. %) and substrate temperature (T{sub s} = 300–550 °C), we fabricated epitaxial FePd films of thickness 20 ± 2 nm by sputtering on MgO (100) single-crystal substrates. The ordering parameter, measured by x-ray diffraction with synchrotron radiation, and the perpendicular anisotropy of the Fe{sub 54}Pt{sub 46} films increased with increasing substrate temperature. For FePd films (T{sub s} = 550 °C) with varied Fe content, a direct correlation between the ordering parameter and the magnetocrystalline anisotropy field is found. The greatest ordering parameter, 0.84, and magnetocrystalline anisotropy field, ∼20 kOe, were obtained formore » FePd films of Fe concentration 54 at. %, indicating that an off-stoichiometric L1{sub 0} FePd might be preferable for engineering and applications.« less
  • Single crystals of the thallium ruthenium pyrochlore have been grown by flux method under high oxygen pressure. The growth conditions were determined by direct observations using in situ powder X-ray diffraction (XRD) method under high pressure and high temperature. The crystals were grown using NaCl-KCl flux at 1350 deg. C and B{sub 2}O{sub 3} flux at 1150 deg. C. High growth temperature of 1350 deg. C for the NaCl-KCl flux caused Pt contamination from the crucible and oxygen deficiency for the crystals obtained. The crystal growth using B{sub 2}O{sub 3} flux proceeded at lower temperature by grain growth with materialmore » transfer through B{sub 2}O{sub 3}. The crystal obtained was characterized by single-crystal XRD method, and was found to have a stoichiometric composition, Tl{sub 2}Ru{sub 2}O{sub 7-} {sub {delta}} ({delta}=0), with a structural phase transition around 120 K. The grain growth technique with B{sub 2}O{sub 3} is efficient for high-temperature single-crystal growth under high pressure.« less