Al Flux Synthesis of the Oxidation-Resistant Quaternary Phase REFe4Al9Si6 (RE = Tb, Er)

作者：Sieve Bradley; Gray Danielle L; Henning Robert; Bakas Thomas; Schultz Arthur J; Kanatzidis Mercouri G^*

来源：Chemistry of Materials, 2008, 20(19): 6107-6115.

DOI：10.1021/cm801554d

Two rare earth iron aluminium silicides, REFe4Al9Si6 (RE = Tb, Er), were synthesized in liquid Al at temperatured below 850 degrees C. They crystallize in the tetragonal space group P4(2)/mnc (no. 137) with cell dimensions of a = 8.718(1) angstrom and c = 15.171(3) angstrom 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 Al-6 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 Mossbauer 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 mettallurgical processing of advanced aluminum matrix alloys are discussed. Thermal gravimetric analysis experiments in air show that REFe4Al9Si6 is resistant to oxidation up to 900 degrees C, Which is attributable to an alumina/silica surface scale.

• 出版日期2008-10-14
• 单位西北大学