Department of Physics, ¶Center of Electron Microscope, and ∥State Key Lab of Silicon Materials, Zhejiang University , Hangzhou 310027, China.
J Am Chem Soc. 2014 Oct 29;136(43):15386-93. doi: 10.1021/ja508564s. Epub 2014 Oct 14.
We have synthesized a novel europium bismuth sulfofluoride, Eu3Bi2S4F4, by solid-state reactions in sealed evacuated quartz ampules. The compound crystallizes in a tetragonal lattice (space group I4/mmm, a = 4.0771(1) Å, c = 32.4330(6) Å, and Z = 2), in which CaF2-type Eu3F4 layers and NaCl-like BiS2 bilayers stack alternately along the crystallographic c axis. There are two crystallographically distinct Eu sites, Eu(1) and Eu(2) at the Wyckoff positions 4e and 2a, respectively. Our bond valence sum calculation, based on the refined structural data, indicates that Eu(1) is essentially divalent, while Eu(2) has an average valence of ∼ +2.64(5). This anomalous Eu valence state is further confirmed and supported, respectively, by Mössbauer and magnetization measurements. The Eu(3+) components donate electrons into the conduction bands that are mainly composed of Bi 6px and 6py states. Consequently, the material itself shows metallic conduction and superconducts at 1.5 K without extrinsic chemical doping.
我们通过在密封的抽空石英管中的固态反应合成了一种新型的铕铋硫化氟化物，Eu3Bi2S4F4。该化合物在四方晶格（空间群 I4/mmm，a = 4.0771(1) Å，c = 32.4330(6) Å，Z = 2）中结晶，其中 CaF2 型 Eu3F4 层和 NaCl 型 BiS2 双层沿晶轴交替堆叠。有两个晶位不同的 Eu 位点，Eu(1)和 Eu(2)分别位于 Wyckoff 位置 4e 和 2a。我们的键价和计算基于精修结构数据，表明 Eu(1)基本上是二价的，而 Eu(2)的平均价态约为+2.64(5)。这种异常的 Eu 价态分别通过穆斯堡尔和磁化测量得到进一步证实和支持。Eu(3+)组分将电子贡献到主要由 Bi 6px 和 6py 态组成的导带中。因此，该材料本身在没有外部分子掺杂的情况下表现出金属导电性，并在 1.5 K 下超导。
