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Charge carrier concentration and mobility in alkali silicates
Jean-Louis Souquet1, Marcio Luis Ferreira Nascimento, Ana Candida Martins Rodrigues
1Laboratoire d'Electrochimie et de Physicochimie des Matériaux et des Interfaces, ENSEEG, BP 75, Saint Martin D'Hères Cedex 38402, France.
The Journal of Chemical Physics
|January 26, 2010
Summary
This study quantifies charge carrier concentration and mobility in glasses by analyzing ionic conductivity. Results reveal distinct temperature-dependent mechanisms influencing conductivity, crucial for understanding glass properties.
Area of Science:
- Materials Science
- Solid State Chemistry
- Physical Chemistry
Background:
- The interplay between charge carrier concentration and mobility in determining ionic conductivity of glasses is not fully understood.
- Ionic conductivity in glasses is influenced by temperature, particularly around the glass transition temperature, T(g).
Purpose of the Study:
- To calculate charge carrier concentration and mobility from conductivity data as a function of temperature.
- To investigate the mechanisms governing ionic displacement in glasses below and above T(g).
Main Methods:
- Formulating expressions for ionic conductivity variation with temperature in glassy and supercooled states.
- Fitting experimental data to proposed expressions to determine characteristic parameters like formation and migration enthalpies.
- Calculating charge carrier concentration and mobility across the entire temperature range.
Main Results:
- Developed a model to differentiate between temperature-activated and free volume mechanisms for ionic migration.
- Determined characteristic parameters including charge carrier formation and migration enthalpies.
- Estimated room temperature mobility of effective charge carriers in alkali disilicate glasses to be ~10(-4) cm(2) s(-1) V(-1).
Conclusions:
- The ratio of effective charge carriers to total alkali cations is very low (10(-8) to 10(-10)).
- This ratio is comparable to intrinsic defect concentrations in ionic crystals or weak electrolyte solutions.
- The study provides a quantitative framework for understanding ionic conductivity in glasses.
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