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Title: Structural investigation of oxygen non-stoichiometry and cation doping in misfit-layered thermoelectric (Ca{sub 2}CoO{sub 3-} {sub x} )(CoO{sub 2}) {sub {delta}} , {delta}{approx}1.61

Abstract

The chemical and crystallographic natures of oxygen non-stoichiometry and cation doping in the 'misfit-layered' cobaltate [Ca{sub 2}CoO{sub 3-} {sub x} ][CoO{sub 2}] {sub {delta}} , {delta}{approx}1.61, were investigated. Single-phase polycrystalline samples were prepared with the help of a high-energy planetary ball mill, and single crystals grown from a K{sub 2}CO{sub 3}/KCl flux. Polycrystalline undoped, Ti{sup 4+}-doped, and Nd{sup 3+}-doped samples were annealed under both air and under argon in order to modify the oxygen non-stoichiometry. The incommensurately modulated composite crystal structures of undoped and Ti{sup 4+}-doped single crystals were refined against X-ray diffraction data using the superspace group X2/m(0,{delta},0)s0. For the as-made (air-annealed) undoped crystal, 14(2)% oxygen vacancies were found on the disordered O2 site in the central layer of the rock-salt-type subsystem, giving an overall stoichiometry [Ca{sub 2}CoO{sub 2.86}][CoO{sub 2}]{sub 1.61}. For the Ti{sup 4+}-doped crystal this site was found to be almost fully occupied, while Ti{sup 4+}-dopant cations were located on the disordered Co1 site in the central layer of the rock-salt-type subsystem, giving an overall formula [Ca{sub 2}Co{sub 0.74}Ti{sub 0.26}O{sub 2.98}][CoO{sub 2}]{sub 1.61}. In both cases, the average cobalt oxidation state is 3.13+. The single-crystal refinements, thermogravimetric analyses and variations in the lattice parameters of polycrystalline samplesmore » refined against synchrotron X-ray diffraction (XRD) data indicate that for both undoped and Ti{sup 4+}-doped samples, substantial numbers of additional oxygen vacancies (15-20%) can be introduced on this site by annealing under an inert atmosphere. Nd{sup 3+}-doped samples have a much lower tolerance (<5%) for oxygen vacancies. - Graphical abstract: The incommensurately modulated composite structure of [Ca{sub 2}CoO{sub 2.86}][CoO{sub 2}]{sub 1.61}.« less

Authors:
 [1];  [2];  [2];  [2]
  1. School of Chemistry, University of Sydney, Sydney, NSW 2006 (Australia) and Bragg Institute, ANSTO, PMB 1, Menai, NSW 2234 (Australia), E-mail: c.ling@chem.usyd.edu.au
  2. School of Chemistry, University of Sydney, Sydney, NSW 2006 (Australia)
Publication Date:
OSTI Identifier:
21015795
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 180; Journal Issue: 4; Other Information: DOI: 10.1016/j.jssc.2007.02.016; PII: S0022-4596(07)00090-4; Copyright (c) 2007 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:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ANNEALING; ARGON; CALCIUM OXIDES; COBALT OXIDES; CRYSTALLOGRAPHY; DOPED MATERIALS; INERT ATMOSPHERE; LATTICE PARAMETERS; MONOCRYSTALS; NEODYMIUM IONS; OXYGEN; POLYCRYSTALS; SALT DEPOSITS; STOICHIOMETRY; THERMAL GRAVIMETRIC ANALYSIS; TITANIUM IONS; VACANCIES; X-RAY DIFFRACTION

Citation Formats

Ling, Chris D., Aivazian, Karina, Schmid, Siegbert, and Jensen, Paul. Structural investigation of oxygen non-stoichiometry and cation doping in misfit-layered thermoelectric (Ca{sub 2}CoO{sub 3-} {sub x} )(CoO{sub 2}) {sub {delta}} , {delta}{approx}1.61. United States: N. p., 2007. Web. doi:10.1016/j.jssc.2007.02.016.
Ling, Chris D., Aivazian, Karina, Schmid, Siegbert, & Jensen, Paul. Structural investigation of oxygen non-stoichiometry and cation doping in misfit-layered thermoelectric (Ca{sub 2}CoO{sub 3-} {sub x} )(CoO{sub 2}) {sub {delta}} , {delta}{approx}1.61. United States. doi:10.1016/j.jssc.2007.02.016.
Ling, Chris D., Aivazian, Karina, Schmid, Siegbert, and Jensen, Paul. Sun . "Structural investigation of oxygen non-stoichiometry and cation doping in misfit-layered thermoelectric (Ca{sub 2}CoO{sub 3-} {sub x} )(CoO{sub 2}) {sub {delta}} , {delta}{approx}1.61". United States. doi:10.1016/j.jssc.2007.02.016.
@article{osti_21015795,
title = {Structural investigation of oxygen non-stoichiometry and cation doping in misfit-layered thermoelectric (Ca{sub 2}CoO{sub 3-} {sub x} )(CoO{sub 2}) {sub {delta}} , {delta}{approx}1.61},
author = {Ling, Chris D. and Aivazian, Karina and Schmid, Siegbert and Jensen, Paul},
abstractNote = {The chemical and crystallographic natures of oxygen non-stoichiometry and cation doping in the 'misfit-layered' cobaltate [Ca{sub 2}CoO{sub 3-} {sub x} ][CoO{sub 2}] {sub {delta}} , {delta}{approx}1.61, were investigated. Single-phase polycrystalline samples were prepared with the help of a high-energy planetary ball mill, and single crystals grown from a K{sub 2}CO{sub 3}/KCl flux. Polycrystalline undoped, Ti{sup 4+}-doped, and Nd{sup 3+}-doped samples were annealed under both air and under argon in order to modify the oxygen non-stoichiometry. The incommensurately modulated composite crystal structures of undoped and Ti{sup 4+}-doped single crystals were refined against X-ray diffraction data using the superspace group X2/m(0,{delta},0)s0. For the as-made (air-annealed) undoped crystal, 14(2)% oxygen vacancies were found on the disordered O2 site in the central layer of the rock-salt-type subsystem, giving an overall stoichiometry [Ca{sub 2}CoO{sub 2.86}][CoO{sub 2}]{sub 1.61}. For the Ti{sup 4+}-doped crystal this site was found to be almost fully occupied, while Ti{sup 4+}-dopant cations were located on the disordered Co1 site in the central layer of the rock-salt-type subsystem, giving an overall formula [Ca{sub 2}Co{sub 0.74}Ti{sub 0.26}O{sub 2.98}][CoO{sub 2}]{sub 1.61}. In both cases, the average cobalt oxidation state is 3.13+. The single-crystal refinements, thermogravimetric analyses and variations in the lattice parameters of polycrystalline samples refined against synchrotron X-ray diffraction (XRD) data indicate that for both undoped and Ti{sup 4+}-doped samples, substantial numbers of additional oxygen vacancies (15-20%) can be introduced on this site by annealing under an inert atmosphere. Nd{sup 3+}-doped samples have a much lower tolerance (<5%) for oxygen vacancies. - Graphical abstract: The incommensurately modulated composite structure of [Ca{sub 2}CoO{sub 2.86}][CoO{sub 2}]{sub 1.61}.},
doi = {10.1016/j.jssc.2007.02.016},
journal = {Journal of Solid State Chemistry},
number = 4,
volume = 180,
place = {United States},
year = {Sun Apr 15 00:00:00 EDT 2007},
month = {Sun Apr 15 00:00:00 EDT 2007}
}