Dissociation Equilibrium and Charge Carrier Formation in AgI–AgPO3 Glasses

• Published in: Journal of physical chemistry. C 2017-06, Vol.121 (25), p.13507-13514
• Main Authors: Bragatto, Caio Barca, Rodrigues, Ana Candida Martins, Souquet, Jean-Louis
• Format: Article
• Language: English
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.7b02477

The xAgI–(1 – x)­AgPO3 glass system exhibits a wide and well-known range of variation in silver ion conductivity with the AgI molar ratio, x, while the total concentration of Ag+ ions does not change significantly. We propose an interpretation to explain this effect, based on the fact that only a fraction of Ag+ cations are effective charge carriers and that their concentration is determined by a dissociation equilibrium of AgI in the AgPO3 glass. In this case, the ionic conductivity stems from the thermodynamic activity of silver iodide, a AgI, dissolved in the AgPO3 glass. To verify this relationship experimentally, a AgI is determined from electromotive force measurements of solid-state cells in the temperature range of 25–90 °C. Our results reveal a linear dependence of silver ion conductivity on a AgI over 3 orders of magnitude. The substantial variations in a AgI observed with the increase in the AgI molar ratio x are justified assuming a regular solution model for the AgI–AgPO3 mixture.