Relaxation dynamics and ionic conductivity in a fragile plastic crystal.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Physical Chemistry

Background:

• Plastic crystals offer unique properties for materials applications.
• Understanding dielectric relaxation and ionic conductivity is crucial for developing new materials.
• Glass formers exhibit complex relaxational dynamics influenced by their structure.

Purpose of the Study:

• To comprehensively characterize the dielectric relaxation and ionic conductivity of a 60% succinonitrile and 40% glutaronitrile mixture.
• To investigate the relaxational behavior across liquid, plastic crystalline, and glassy crystal phases.
• To assess the material's potential as a solid-state electrolyte.

Main Methods:

• Broadband dielectric spectroscopy was employed to study the material's response.
• Analysis focused on identifying and characterizing different relaxation processes (α, secondary, and potential Johari-Goldstein).
• Ionic conductivity contributions were quantified from the dielectric spectra.

Main Results:

• The study detailed the α-relaxation process and identified a distinct secondary relaxation, with hints of a third (Johari-Goldstein type).
• A fragility parameter of 62 was determined, classifying the material as a relatively fragile glass former.
• Significant ionic conductivity contributions, characteristic of ionic charge transport, were observed.

Conclusions:

• The succinonitrile-glutaronitrile mixture demonstrates fragile glass-forming behavior, supporting energy-landscape theories.
• The observed strong ionic conductivity makes this material a promising candidate for solid-state electrolyte applications.
• Further research into plastic crystalline electrolytes is warranted based on these findings.