The Local Atomic Structure and Chemical Bonding in Sodium Tin Phases
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Univ. Montpellier II (France)
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)
To understand these electrochemically-derived materials we have reinvestigated the formation of Na-Sn alloys to identify all the phases which form when x ≥ 1 (NaxSn) and characterized the local bonding around the Sn atoms with X-ray diffraction, 119Sn M ssbauer spectroscopy, and X-ray absorption spectroscopies. The results from the well-defined crystallographic materials were compared to the spectroscopic measurements of the local Sn structures in the electrochemically prepared materials. The reinvestigation of the Na-Sn compounds yields a number of new results: (i) Na7Sn3 is a new thermodynamically-stable phase with a rhombohedral structure and R-3m space group; (ii) orthorhombic Na9Sn4 (Cmcm) has relatively slow formation kinetics suggesting why it does not form at room temperature during the electrochemical reaction; (iii) orthorhombic Na14.78Sn4 (Pnma), better described as Na16-xSn4, is Na-richer than cubic Na15Sn4 (I-43d). Characterization of electrochemically prepared Na-Sn alloys indicate that, at the exception of Na7Sn3 and Na15Sn4, different crystal structures than similar Na-Sn compositions prepared via classic solid state reactions are formed. These phases are composed of disordered structures characteristic of kinetic-driven solid-state amorphization reactions. In these structures, Sn coordinates in asymmetric environments, which differ significantly from the environments present in Na-Sn model compounds.
- Research Organization:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- Grant/Contract Number:
- AC05-00OR22725
- OSTI ID:
- 1185716
- Journal Information:
- Journal of Materials Chemistry. A, Vol. 2, Issue 44; ISSN 2050-7488
- Publisher:
- Royal Society of ChemistryCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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