Similarities and differences in the structural and electronic properties of ruthenium and iridium pyrochlores A{sub 2}M{sub 2}O{sub 7{minus}y} (M = Ru, Ir)

Journal Article · Sun Mar 01 04:00:00 EST 1998 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1006/jssc.1997.7705· OSTI ID:642173

Koo, H J; Whangbo, M H ^[1]; Kennedy, B J ^[2]

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1. North Carolina State Univ., Raleigh, NC (United States). Dept. of Chemistry
2. Univ. of Sydney, New South Wales (Australia). School of Chemistry

Electronic band structures of the ruthenium and iridium pyrochlores A{sub 2}M{sub 2}O{sub 6}O{sub 1{minus}y}{prime} (M = Ru, Ir) were examined using the extended Hueckel tight-binding method. The metal versus semiconductor behaviors of these pyrochlores are explained in terms of the Mott-Hubbard localization concept. The M-O, A-O, and A-O{prime} distances and M-O-M angles of A{sub 2}M{sub 2}O{sub 6}O{sub 1{minus}y}{prime} (M = Ru, Ir) were analyzed in terms of the A cation ionic radius. The M-O distance and the M-O-M angle are strongly influenced by the overlap repulsion between the filled shells of the A cation and O{sup 2{minus}} anions. The O{prime} vacancies of the pyrochlores A{sub 2}M{sub 2}O{sub 6}O{sub 1{minus}y}{prime} with polarizable A cations such as Tl{sup +}, Pb{sup 2+}, or Bi{sup 3+} occur most likely to reduce the overlap repulsion associated with the 6s orbitals of the A cations.

• OSTI ID: 642173
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 2 Vol. 136; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BOND ANGLE
BOND LENGTHS
CRYSTAL STRUCTURE
ELECTRICAL PROPERTIES
IRIDIUM OXIDES
PYROCHLORE
RUTHENIUM OXIDES
THEORETICAL DATA