Synthesis,structure and optical properties of new lanthanide-based derivatives Ln2SbS5Br (Ln=La,Ce) |
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| Institution: | 1. Department of Materials Forming and Control Engineering, Faculty of Mechanical Engineering & Automation, Zhejiang Sci-Tech University, Hangzhou 310018, People’s Republic of China;2. College of Materials and Textiles, Zhejiang Sci-Tech University, Hangzhou 310018, People’s Republic of China;1. Key Laboratory of Materials Physics, Anhui Key Laboratory of Nanomaterials and Nanotechnology, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, PR China;2. University of Science and Technology of China, Hefei 230026, PR China;1. Institute of Physics, University of Tartu, W. Ostwald Str. 1, Tartu 50411, Estonia;2. CERN, Geneva 23, CH-1211, Switzerland;3. Skobeltsyn Institute of Nuclear Physics, Moscow State University, 1(2), Leninskie gory, GSP-1, Moscow 119991, Russia;4. National University of Science and Technology (MISiS), Leninsky Prospekt 4, Moscow 119049, Russia |
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| Abstract: | The first bromothioantimonates of cerium and lanthanum, Ce2SbS5Br (I), CeLaSbS5Br (II) and La2SbS5Br (III), have been synthesized and characterized. I and III crystallize in the Pnma (n°62) space group while the structure of II was refined in the P212121 (n°19) space group probably due to an ordering between Ce and La. The cell parameters are: a=8.847(2) Å, b=5.492(1) Å, c=17.697(6) Å, V=859.9(6) Å3 for I; a=8.9023(9) Å, b=5.5113(6) Å, c=17.809(2) Å, V=873.8(3) Å3 for II and a=8.905(2) Å, b=5.526(1) Å, c=17.883(3) Å, V=880.0(5) Å3 for III. These three materials exhibit the same novel structural arrangement with lanthanides surrounded by sulfur and bromine anions in two different LnS7Br3 and LnS8Br units. Some sulfur atoms are engaged in SS bonding dimers while antimony exhibits a SbS4E coordination (E=lone pair), the characteristics of which hint at a stereo-active 5s2 electron pair. The charge balance in the materials is written as LnIII2SbIII(S2)–IIS–II3Br. The same red color of the three materials rules out the occurrence of the Ce-4f1→Ce-5d1 electronic transition usually observed in Ce containing sulfides. In contrast, band structure calculations (TB-LMTO-ASA) assigned the observed absorption threshold around 2.08 eV for the three phases to the existence of a VB→CB electronic transition, i.e. an unpaired S or Br→Sb or paired S charge transfer. |
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