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Title: Partial oxygen ordering in cubic perovskite REBa{sub 2}Fe{sub 3}O{sub 8+w} (RE = Gd, Eu, Sm, Nd)

Abstract

Single-phase samples of cubic REBa{sub 2}Fe{sub 3}O{sub 8+w} with RE = Gd, Eu, Sm, Nd were synthesized and equilibrated at 900 C in atmospheres with controlled partial pressures of oxygen. The oxygen content parameter w ranged from approximately {minus}0.30, which is the lower decomposition limit, to between w = 0.17 for RE = Gd and w = 0.37 for RE = Nd, achieved in O{sub 2} without crossing the upper limit. According to {sup 57}Fe Moessbauer spectroscopy, all samples are antiferromagnets at room temperature, with iron in high-spin states (S = 2 for Fe{sup 2+} and Fe{sup 4+}; S = 5/2 for Fe{sup 3+}). The contents of divalent or, alternatively, tetravalent iron states are consistent with the stoichiometry of the samples. At the stoichiometric composition (w = 0), all Moessbauer components correspond to trivalent iron, differing only in the coordination geometries of their oxygen neighborhoods. The sum-up of the observed coordination number shows that the oxygen disorder in these cubic (by X-ray diffraction) phases is a linear combination of the two limiting cases of oxygen vacancy distribution: binomial (random) and ordered (one vacancy per every third pseudocubic cell). This corresponds to a gradual change from the long-range order seen inmore » triple-perovskite-type phases (RE = Er to Dy) via a short-range order seen in the present systems (RE = Gd to Nd) to a fully random disorder (RE = La). Eventual variations in w affect the coordination statistics in details, but change the overall picture very little.« less

Authors:
 [1]; ;  [2]; ;  [3]
  1. Aabo Akademi, Turku (Finland). Dept. of Physics
  2. Univ. of Oslo (Norway). Dept. of Chemistry
  3. Helsinki Univ. of Technology, Espoo (Finland)
Publication Date:
OSTI Identifier:
351519
Resource Type:
Journal Article
Journal Name:
Journal of Solid State Chemistry
Additional Journal Information:
Journal Volume: 144; Journal Issue: 2; Other Information: PBD: May 1999
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CRYSTAL STRUCTURE; GADOLINIUM OXIDES; EUROPIUM OXIDES; SAMARIUM OXIDES; NEODYMIUM OXIDES; BARIUM OXIDES; IRON OXIDES; STOICHIOMETRY; SPECTROSCOPY; ORDER PARAMETERS; EXPERIMENTAL DATA

Citation Formats

Linden, J, Karen, P, Kjekshus, A, Miettinen, J, and Karppinen, M. Partial oxygen ordering in cubic perovskite REBa{sub 2}Fe{sub 3}O{sub 8+w} (RE = Gd, Eu, Sm, Nd). United States: N. p., 1999. Web. doi:10.1006/jssc.1999.8178.
Linden, J, Karen, P, Kjekshus, A, Miettinen, J, & Karppinen, M. Partial oxygen ordering in cubic perovskite REBa{sub 2}Fe{sub 3}O{sub 8+w} (RE = Gd, Eu, Sm, Nd). United States. doi:10.1006/jssc.1999.8178.
Linden, J, Karen, P, Kjekshus, A, Miettinen, J, and Karppinen, M. Sat . "Partial oxygen ordering in cubic perovskite REBa{sub 2}Fe{sub 3}O{sub 8+w} (RE = Gd, Eu, Sm, Nd)". United States. doi:10.1006/jssc.1999.8178.
@article{osti_351519,
title = {Partial oxygen ordering in cubic perovskite REBa{sub 2}Fe{sub 3}O{sub 8+w} (RE = Gd, Eu, Sm, Nd)},
author = {Linden, J and Karen, P and Kjekshus, A and Miettinen, J and Karppinen, M},
abstractNote = {Single-phase samples of cubic REBa{sub 2}Fe{sub 3}O{sub 8+w} with RE = Gd, Eu, Sm, Nd were synthesized and equilibrated at 900 C in atmospheres with controlled partial pressures of oxygen. The oxygen content parameter w ranged from approximately {minus}0.30, which is the lower decomposition limit, to between w = 0.17 for RE = Gd and w = 0.37 for RE = Nd, achieved in O{sub 2} without crossing the upper limit. According to {sup 57}Fe Moessbauer spectroscopy, all samples are antiferromagnets at room temperature, with iron in high-spin states (S = 2 for Fe{sup 2+} and Fe{sup 4+}; S = 5/2 for Fe{sup 3+}). The contents of divalent or, alternatively, tetravalent iron states are consistent with the stoichiometry of the samples. At the stoichiometric composition (w = 0), all Moessbauer components correspond to trivalent iron, differing only in the coordination geometries of their oxygen neighborhoods. The sum-up of the observed coordination number shows that the oxygen disorder in these cubic (by X-ray diffraction) phases is a linear combination of the two limiting cases of oxygen vacancy distribution: binomial (random) and ordered (one vacancy per every third pseudocubic cell). This corresponds to a gradual change from the long-range order seen in triple-perovskite-type phases (RE = Er to Dy) via a short-range order seen in the present systems (RE = Gd to Nd) to a fully random disorder (RE = La). Eventual variations in w affect the coordination statistics in details, but change the overall picture very little.},
doi = {10.1006/jssc.1999.8178},
journal = {Journal of Solid State Chemistry},
number = 2,
volume = 144,
place = {United States},
year = {1999},
month = {5}
}