Routes to the quaternary aluminum silicides RE4FE2+xAl7-xSi8 (RE = Ce, Pr, Nd, Sm); exploratory synthesis with molten Al as a solvent

B. Sieve, S. Sportouch, X. Z. Chen, J. A. Cowen, P. Brazis, C. R. Kannewurf, V. Papaefthymiou, Mercouri G Kanatzidis

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Abstract

The four new intermetallic aluminum silicides RE4Fe2+xAl7-xSi8 (RE = Ce, Pr, Nd, Sm) crystallize from the reaction of Si, Fe, and RE (or rare earth oxides) in molten Al at 850 °C. All compounds share the same structure type as determined by single-crystal X-ray diffraction analysis. They form in the space group Cmmm (No. 65) with cell constants of a = 10.909(2) Å, b = 16.265(3) Å, c = 4.0804(8) Å, R1 = 0.0196, and wR2 = 0.0486 for the Sm analogue. The crystal structure is a complex three-dimensional network comprised of repeating layers containing Al, Si, and Fe connected by atoms between the layers. The RE3+ ions are then located within tunnels of the three-dimensional network, running parallel to the c axis with a coordination number of 14. Magnetic susceptibility measurements indicate that the rare earth ions are in a 3+ oxidation state, whereas the Fe atoms are in an effective diamagnetic state. Electronic band structure calculations, carried out on the hypothetical analogue Y4Fe2Al7Si8, predict metallic behavior and suggest Fe to be in a reduced state with almost filled d orbitals. Variable temperature electrical conductivity and thermopower measurements confirm the metallic nature of the compounds. The charge transport and magnetic properties of the Ce analogue are anomalous and indicative of f1/0 valence fluctuations at T <100 K.

Original languageEnglish
Pages (from-to)273-283
Number of pages11
JournalChemistry of Materials
Volume13
Issue number2
DOIs
Publication statusPublished - 2001

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Silicides
Aluminum
Oxides
Rare earths
Molten materials
Ions
Atoms
Thermoelectric power
Magnetic susceptibility
Band structure
Transport properties
X ray diffraction analysis
Intermetallics
Charge transfer
Magnetic properties
Tunnels
Crystal structure
Single crystals
Oxidation
Temperature

ASJC Scopus subject areas

  • Materials Chemistry
  • Materials Science(all)

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Routes to the quaternary aluminum silicides RE4FE2+xAl7-xSi8 (RE = Ce, Pr, Nd, Sm); exploratory synthesis with molten Al as a solvent. / Sieve, B.; Sportouch, S.; Chen, X. Z.; Cowen, J. A.; Brazis, P.; Kannewurf, C. R.; Papaefthymiou, V.; Kanatzidis, Mercouri G.

In: Chemistry of Materials, Vol. 13, No. 2, 2001, p. 273-283.

Research output: Contribution to journalArticle

Sieve, B. ; Sportouch, S. ; Chen, X. Z. ; Cowen, J. A. ; Brazis, P. ; Kannewurf, C. R. ; Papaefthymiou, V. ; Kanatzidis, Mercouri G. / Routes to the quaternary aluminum silicides RE4FE2+xAl7-xSi8 (RE = Ce, Pr, Nd, Sm); exploratory synthesis with molten Al as a solvent. In: Chemistry of Materials. 2001 ; Vol. 13, No. 2. pp. 273-283.
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abstract = "The four new intermetallic aluminum silicides RE4Fe2+xAl7-xSi8 (RE = Ce, Pr, Nd, Sm) crystallize from the reaction of Si, Fe, and RE (or rare earth oxides) in molten Al at 850 °C. All compounds share the same structure type as determined by single-crystal X-ray diffraction analysis. They form in the space group Cmmm (No. 65) with cell constants of a = 10.909(2) {\AA}, b = 16.265(3) {\AA}, c = 4.0804(8) {\AA}, R1 = 0.0196, and wR2 = 0.0486 for the Sm analogue. The crystal structure is a complex three-dimensional network comprised of repeating layers containing Al, Si, and Fe connected by atoms between the layers. The RE3+ ions are then located within tunnels of the three-dimensional network, running parallel to the c axis with a coordination number of 14. Magnetic susceptibility measurements indicate that the rare earth ions are in a 3+ oxidation state, whereas the Fe atoms are in an effective diamagnetic state. Electronic band structure calculations, carried out on the hypothetical analogue Y4Fe2Al7Si8, predict metallic behavior and suggest Fe to be in a reduced state with almost filled d orbitals. Variable temperature electrical conductivity and thermopower measurements confirm the metallic nature of the compounds. The charge transport and magnetic properties of the Ce analogue are anomalous and indicative of f1/0 valence fluctuations at T <100 K.",
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