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Ionic conductivity and glass transition of phosphoric acids
Yangyang Wang1, Nathan A Lane, Che-Nan Sun
1Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA. wangy@ornl.gov
The Journal of Physical Chemistry. B
|June 15, 2013
Summary
We studied phosphoric acids using dielectric and viscosity measurements to find their glass-transition temperatures. Results show ionic conductivity and structural relaxation behave differently near this transition.
Area of Science:
- Materials Science
- Physical Chemistry
- Condensed Matter Physics
Background:
- Phosphoric acids are important in various chemical processes.
- Understanding their properties, especially at low temperatures, is crucial for applications.
- Glass-transition phenomena in such materials are complex and require detailed investigation.
Purpose of the Study:
- To investigate the low-temperature dielectric and viscoelastic properties of phosphoric acids.
- To determine the glass-transition temperatures (Tg) of phosphoric acids using multiple methods.
- To explore the relationship between ionic conductivity and structural relaxation near Tg.
Main Methods:
- Low-temperature dielectric spectroscopy.
- Viscosity measurements.
- Analysis of H2O:P2O5 ratios from 1.5 to 5.
Main Results:
- Dielectric and viscosity measurements successfully determined glass-transition temperatures.
- Obtained Tg values align well with previous differential scanning calorimetry data.
- Observed moderate decoupling between ionic conductivity and structural relaxation near the glass transition.
Conclusions:
- Dielectric and viscoelastic properties provide reliable methods for determining Tg in phosphoric acids.
- The study confirms the agreement between different thermal analysis techniques.
- Evidence of decoupling highlights the complex dynamics governing ion transport and structural rearrangements in these systems.
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