A microscopic interpretation of the bulk anomalies in AgI–Ag₂O · 2B₂O₃ glasses

Abstract

The glassy system xAgI:(1 − x)Ag₂O · 2B₂O₃ is characterized by anomalies of several quantities (glass transition temperature, density, molar volume) in the composition region 0.3 ≤ x ≤ 0.4. Here, we interpret these anomalies in the framework of a recent percolation model we proposed to explain the transport properties of AgI-based fast ion conducting glasses. The key point of the model is that the mobility of the silver cations is related to their mixed oxygen–iodine coordination. We show that all the observed anomalies are conveniently explained by considering the transition, interesting both in the short and the medium range, between a composition region where isolated clusters of O–Ag–I sites are present (x < 0.3), and a region where fully interconnected pathways of O–Ag–I sites are created (x > 0.4).

Acknowledgements

This work has been performed in the frame of a PRIN Project (M. Cutroni leading, 2004). Some discussions with M. Cutroni and F. Rocca are gratefully acknowledged.