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Title: Strontium ordering, structural modulation in layered hexagonal Sr {sub x}CoO{sub 2} and physical properties of Sr{sub 0.35}CoO{sub 2}

Abstract

Layered Sr{sub 0.35}CoO{sub 2} has been synthesized by means of an ion exchange reaction from Na{sub 0.7}CoO{sub 2}. Resistivity measurements show that this material can be either metallic or semiconducting depending on the annealing conditions. The magnetic susceptibility of the sample increases with decreasing temperature, showing a Curie-Weiss behavior in high temperatures. Transmission electron microscopy observations reveal the presence of two superstructures arising respectively from the intercalated Sr-ordering (a compositional modulation) with q {sub 1} = a*/3 + b*/3 and a periodic structural distortion (a transverse structural modulation) with q {sub 2} = a*/2.

Authors:
 [1];  [2];  [2];  [2];  [2];  [2];  [2]
  1. Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China). E-mail: hxyang@blem.ac.cn
  2. Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China)
Publication Date:
OSTI Identifier:
20900949
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Research Bulletin; Journal Volume: 42; Journal Issue: 1; Other Information: DOI: 10.1016/j.materresbull.2006.05.007; PII: S0025-5408(06)00205-4; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ANNEALING; COBALT OXIDES; INORGANIC COMPOUNDS; ION EXCHANGE; MAGNETIC SUSCEPTIBILITY; MICROSTRUCTURE; MODULATION; PERIODICITY; STRONTIUM; STRONTIUM OXIDES; TRANSMISSION ELECTRON MICROSCOPY

Citation Formats

Yang, H.X., Shi, Y.G., Guo, Y.Q., Liu, X., Xiao, R.J., Luo, J.L., and Li, J.Q.. Strontium ordering, structural modulation in layered hexagonal Sr {sub x}CoO{sub 2} and physical properties of Sr{sub 0.35}CoO{sub 2}. United States: N. p., 2007. Web. doi:10.1016/j.materresbull.2006.05.007.
Yang, H.X., Shi, Y.G., Guo, Y.Q., Liu, X., Xiao, R.J., Luo, J.L., & Li, J.Q.. Strontium ordering, structural modulation in layered hexagonal Sr {sub x}CoO{sub 2} and physical properties of Sr{sub 0.35}CoO{sub 2}. United States. doi:10.1016/j.materresbull.2006.05.007.
Yang, H.X., Shi, Y.G., Guo, Y.Q., Liu, X., Xiao, R.J., Luo, J.L., and Li, J.Q.. Thu . "Strontium ordering, structural modulation in layered hexagonal Sr {sub x}CoO{sub 2} and physical properties of Sr{sub 0.35}CoO{sub 2}". United States. doi:10.1016/j.materresbull.2006.05.007.
@article{osti_20900949,
title = {Strontium ordering, structural modulation in layered hexagonal Sr {sub x}CoO{sub 2} and physical properties of Sr{sub 0.35}CoO{sub 2}},
author = {Yang, H.X. and Shi, Y.G. and Guo, Y.Q. and Liu, X. and Xiao, R.J. and Luo, J.L. and Li, J.Q.},
abstractNote = {Layered Sr{sub 0.35}CoO{sub 2} has been synthesized by means of an ion exchange reaction from Na{sub 0.7}CoO{sub 2}. Resistivity measurements show that this material can be either metallic or semiconducting depending on the annealing conditions. The magnetic susceptibility of the sample increases with decreasing temperature, showing a Curie-Weiss behavior in high temperatures. Transmission electron microscopy observations reveal the presence of two superstructures arising respectively from the intercalated Sr-ordering (a compositional modulation) with q {sub 1} = a*/3 + b*/3 and a periodic structural distortion (a transverse structural modulation) with q {sub 2} = a*/2.},
doi = {10.1016/j.materresbull.2006.05.007},
journal = {Materials Research Bulletin},
number = 1,
volume = 42,
place = {United States},
year = {Thu Jan 18 00:00:00 EST 2007},
month = {Thu Jan 18 00:00:00 EST 2007}
}
  • A series of Ca{sub x}CoO{sub 2} (0.15{<=}x{<=}0.40) materials have been prepared by means of an ion exchange reaction from Na{sub x}CoO{sub 2}. Transmission electron microscopy (TEM) measurements revealed a rich variety of structural phenomena resulting from cation ordering, structural distortion, and twinning. Systematic structural analysis, in combination with the experimental data of Na{sub x}CoO{sub 2} (0.15{<=}x{<=}0.8) and Sr{sub x}CoO{sub 2} (1.5{<=}x{<=}0.4) systems, suggests that there are two common well-defined cation ordered states corresponding, respectively, to the orthorhombic superstructure at around x=1/2 and the 3{sup 1/2}ax3{sup 1/2}a superstructure at around x=1/3 in this kind of system. Multiple ordered states, phase separation,more » and incommensurate structural modulations commonly appear in the materials with 0.33<x<0.5. The TEM observations also reveal an additional periodic structural distortion with q{sub 2}=a{sup *}/2 in materials for x{<=}0.35. This structural modulation also appears in the remarkable superconducting phase Na{sub 0.33}CoO{sub 2}{center_dot}1.3H{sub 2}O.« less
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  • Investigations in the Sr-Co-Ga-O system by means of transmission electron microscopy techniques have allowed the detection of a new layered cobaltite. Its structure has been obtained by combining high-resolution images and powder X-ray diffraction. The modulated structure of this novel oxide (Ga{sub 1/3}Co{sub 2/3}){sub 2}Sr{sub 2}CoO{sub 6+{delta}} is derived from the perovskite with a=a{sub p}{radical}2, b=a{sub p}{radical}2, c=19.2A and a modulation vector q*=q{sub 1}a*+q{sub 2}c*. For the as-prepared samples, the {delta} value is close to 0.4 and the modulated structure (q{sub 1}{approx}1/3 and q{sub 2}=1) can be described in an ideal orthorhombic 3D supercell Bb2b with the unit cell parametersmore » a=3a{sub p}{radical}2=16.3030(5)A, b=5.4725(2)A and c=19.2034(4)A. The layer stacking consists in an intergrowth between a [SrCoO{sub 3}] perovskite-type block and a block of triple layers, [(SrO)(Co{sub 2/3}Ga{sub 1/3}O{sub 1+{delta}}{sub /2})(Co{sub 2/3}Ga{sub 1/3}O{sub 1+{delta}}{sub /2})] derived from [AO] rock-salt type layers. The magnetic study shows that the Co{sup 3+} cations exhibit a high spin state in this structure. The {theta}{sub p} value, -570K, suggests that antiferromagnetic interactions dominate in this compound as in the brownmillerite cobaltites. Nonetheless, its resistivity {rho}{sub 300K}=10{sup -1}{omega}cm is lower than that of the brownmillerite compounds. Since the positive Seebeck coefficient indicates the presence of holes (Co{sup 4+}) in the CoO{sub 2} conducting layers, the existence of weak ferromagnetic Co{sup 3+}-O-Co{sup 4+} interactions developing below {approx}150K is proposed to explain the electronic properties of this new oxide.« less
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