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Alkali-Glass Behavior in Honeycomb-Type Layered Li3-NaNi2SbO6 Solid Solution
Coélio Vallée1, Matthieu Saubanère1,2, Paula Sanz-Camacho2,3
1ICGM, Universite' de Montpellier, CNRS , 34095 Montpellier , France.
Inorganic Chemistry
|August 23, 2019
Summary
Researchers synthesized novel Li-Na layered oxides, revealing an unusual disordered alkali layer. This alkali glass, trapped by fast cooling, offers new possibilities for advanced materials.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Crystallography
Background:
- Layered oxide materials are crucial for various applications, including energy storage and catalysis.
- Understanding the precise atomic arrangement within these structures is key to tailoring their properties.
Purpose of the Study:
- To synthesize and characterize novel layered oxide compositions within the Li-Na-Ni-Sb-O system.
- To investigate the ordering and dynamics of alkali metal ions (Li and Na) in the interslab space.
- To explore the influence of synthesis conditions on the resulting crystal structure and alkali distribution.
Main Methods:
- Solid-state synthesis was employed to prepare Li3-xNaxNi2SbO6 compositions.
- X-ray and neutron diffraction techniques were utilized for structural characterization.
- Solid-state nuclear magnetic resonance spectroscopy (7Li and 23Na NMR) was used to probe alkali site occupancy and dynamics.
- In situ X-ray diffraction and density functional theory (DFT) calculations were performed to understand the driving forces for structural features.
Main Results:
- A complete solid solution was successfully synthesized, forming layered oxides with a honeycomb transition-metal layer (Ni2+/Sb5+).
- Uncommon random mixing of lithium and sodium ions was observed in the alkali interslab space.
- In situ studies and DFT calculations indicated that this alkali disorder is entropically driven.
- Fast cooling was identified as a method to "freeze" this disordered alkali state within the crystalline structure, forming a bidimensional alkali glass.
Conclusions:
- The synthesis of Li-Na layered oxides with a disordered alkali interslab space was achieved.
- Entropic effects play a significant role in driving the random distribution of Li and Na ions.
- Fast cooling is an effective strategy to stabilize this unique alkali-disordered structure, creating novel crystalline materials with embedded glassy alkali layers.
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