Ternary rare-earth bismuthides RE₅SiBi₂ and RE₅GeBi₂ (RE=La–Nd, Gd–Er): Stabilization of the β-Yb₅Sb₃-type structure through tetrel substitution

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• 作者：Stephen D. Barry^a ; Andriy V. Tkachuk^a ; Haiying Bie^a ; Peter E.R. Blanchard^a ; Arthur Mar ; ^a ; ^{arthur.mar@ualberta.ca}
• 关键词：Rare earths ; Bismuthides ; Crystal structure ; XPS ; Magnetic properties
• 刊名：Journal of Solid State Chemistry
• 出版年：2011
• 出版时间：January 2011
• 年：2011
• 卷：184
• 期：1
• 页码：21-29
• 全文大小：989 K

文摘

Ternary bismuthides RE₅TtBi₂ containing rare-earth (RE=La–Nd, Gd–Er) and tetrel (Tt=Si, Ge) atoms have been prepared by arc-melting of the elements followed by annealing at 800 °C. They adopt the β-Yb₅Sb₃-type structure (Pearson symbol oP32, space group Pnma, Z=4), as revealed through analysis by single-crystal X-ray diffraction on Ce₅Si_0.869(4)Bi_2.131(4) and powder X-ray diffraction on Ce₅GeBi₂. Cell parameters for the entire series lie in the ranges of a=12.8–11.8 Å, b=9.6–9.0 Å, and c=8.4–7.9 Å. Solid solubility in Ce₅Si_xBi_3−x and Pr₅Si_xBi_3−x (approximately 0.9≤x≤1.2, depending on the RE member) is much more limited compared to the antimonides, consistent with a highly ordered structure in which the two possible anion sites are essentially segregated into a smaller one occupied by Tt atoms (CN7) and a larger one occupied by Bi atoms (CN9). Band structure calculations on La₅SiBi₂ confirm the importance of La–La bonding interactions near the Fermi level. X-ray photoelectron spectra support the presence of partially anionic Bi atoms, as indicated by a small negative binding energy shift relative to elemental Bi. The Ce and Pr members undergo magnetic transitions at low temperatures, possibly involving ferromagnetic interactions, that are strongly influenced by the nature of the Tt atom.