Intricate Short-Range Ordering and Strongly Anisotropic Transport Properties of Li1-x Sn2+x As2
Abstract
A new ternary compound, Li1-x Sn2+x As2 , 0.2 < x < 0.4, was synthesized via solid-state reaction of elements. The compound crystallizes in a layered structure in the R3¯m space group (No. 166) with Sn-As layers separated by layers of jointly occupied Li/Sn atoms. The Sn-As layers are comprised of Sn3 As3 puckered hexagons in a chair conformation that share all edges. Li/Sn atoms in the interlayer space are surrounded by a regular As6 octahedron. Thorough investigation by synchrotron X-ray and neutron powder diffraction indicate no long-range Li/Sn ordering. In contrast, the local Li/Sn ordering was revealed by synergistic investigations via solid-state 6,7Li NMR spectroscopy, HRTEM, STEM, and neutron and X-ray pair distribution function analyses. Due to their different chemical natures, Li and Sn atoms tend to segregate into Li-rich and Sn-rich regions, creating substantial inhomogeneity on the nanoscale. The inhomogeneous local structure has a high impact on the physical properties of the synthesized compounds the local Li/Sn ordering and multiple nanoscale interfaces result in unexpectedly low thermal conductivity and highly anisotropic resistivity in Li1-x Sn2+x As2 . (Graph Presented). © 2015 American Chemical Society.
Keywords
Magnetism
Electron transport
Crystal structure
Conformation
Chemical structure
Chemical reaction
Article
Anisotropy
Tin
Lithium ion
Arsenic
Lithium
Short range ordering
Pair distribution function analysis
Nanoscale interfaces
Low thermal conductivity
Li nmr spectroscopies
Chair conformations
Anisotropic transport
Anisotropic resistivity
Solid state reactions
Nanotechnology
Distribution functions
Atoms
Neutron diffraction
Nuclear magnetic resonance spectroscopy
Oxidation
Scanning transmission electron microscopy
Solid state
Synthesis
Thermal conductivity
Transmission electron microscopy
X ray powder diffraction
Layers