Formation of Amorphous AgI Aggregates Dominating Fast Ion Conductivity in AgI-based Glasses.

Precise calorimetry was performed for (AgI)_x(AgPO₃)_1−x and (AgI)_x(Ag₂PO_3.5)_1−x glasses with very high AgI compositions (x≥0.75). The glasses showed β-glass transitions due to the freezing-in of the rearrangement of conductive Ag⁺ ions. Magnitude of the associated heat-capacity jump increased with increasing the AgI composition in the respective glass systems, and was larger in the former system than in the latter when compared at the same AgI composition. All the results were well explained by the ‘amorphous AgI aggregate’ model for the AgI-based fast ion conducting glasses, indicating the appropriateness of the model for the structure of the glasses with high AgI compositions. The formation of the hypothetical bulk amorphous AgI was also indicated in the glasses at the highest limit of AgI composition. [ABSTRACT FROM AUTHOR]