Al flux synthesis of the oxidation-resistant quaternary phase REFe 4Al9Si6 (RE = Tb, Er)

Bradley Sieve, Danielle L. Gray, Robert Henning, Thomas Bakas, Arthur J. Schultz, Mercouri G. Kanatzidis

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12 Citations (Scopus)

Abstract

Two rare earth iron aluminum silicides, REFe4Al 9Si6 (RE = Tb, Er), were synthesized in liquid Al at temperatures below 850°C. They crystallize in the tetragonal space group P42/nmc (no. 137) with cell dimensions of a = 8.718(1) Å and c = 15.171(3) Å for the Tb analogue. The structure, which is highly intricate and represents a rare structural arrangement, is based on that of NdRh4Al15.4. It can be understood in terms of highly corrugated layers of merged Al6 rings stacking to form a three-dimensional framework. The Fe and Si atoms are situated in various sites in the framework. The RE atoms have a very high coordination number (20) and sit in remaining pockets formed by the bonding arrangements in the structure. Magnetic measurements show that the rare earth ions are in a 3+ state, whereas Mössbauer measurements show that the Fe atoms do not exhibit a magnetic moment and are more reduced than in elemental Fe. The possible insights gained from these results into the metallurgical processing of advanced aluminum matrix alloys are discussed. Thermal gravimetric analysis experiments in air show that REFe4Al9Si6 is resistant to oxidation up to 900°C, which is attributable to an alumina/silica surface scale.

Original languageEnglish
Pages (from-to)6107-6115
Number of pages9
JournalChemistry of Materials
Volume20
Issue number19
DOIs
Publication statusPublished - Oct 14 2008

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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