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Ionic conductivity and relaxation dynamics in plastic crystals with nearly globular molecules
D Reuter1, K Seitz1, P Lunkenheimer1
1Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany.
The Journal of Chemical Physics
|July 10, 2020
Summary
Ionic charge transport in plastic crystals (PCs) like 1-cyano-adamantane (CNA) is decoupled from molecular motion. This study reveals enhanced ionic conductivity and a distinct ionic hopping relaxation in CNA-based solid electrolytes.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Dielectric Spectroscopy
Background:
- Plastic crystals (PCs) are molecular solids with unique properties.
- Ionic conductivity in PCs is often linked to molecular reorientation (revolving-door mechanism).
- 1-cyano-adamantane (CNA) is a plastic crystal with a globular molecular shape.
Purpose of the Study:
- Investigate ionic charge transport and relaxation dynamics in CNA and its mixtures.
- Determine if the revolving-door mechanism is active in CNA.
- Analyze mixing effects on ionic conductivity and relaxation processes.
Main Methods:
- Dielectric spectroscopy was used to study CNA and mixtures with adamantane or 2-adamantanon.
- Li salt was added to provide ionic charge carriers.
- DC resistivity and dielectric loss were measured to probe charge transport and relaxation.
Main Results:
- Complete decoupling of ionic charge transport from molecular reorientational (α) relaxation was observed in CNA.
- A significant mixing-induced enhancement of ionic conductivity was found.
- A secondary relaxation process, attributed to ionic hopping, was clearly detected and separated from α-relaxation.
Conclusions:
- The revolving-door mechanism is not the primary pathway for ionic transport in CNA.
- CNA-based materials exhibit enhanced ionic conductivity upon mixing.
- The distinct ionic hopping relaxation in CNA offers opportunities for designing advanced solid-state electrolytes.
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