Thermal behaviour of the local environment around iodine in fast-ion-conducting AgI-doped glasses

Abstract

The local environment around iodine has been studied as a function of temperature by extended X-ray absorption fine structure (EXAFS) in fast-ion-conducting AgI doped glasses (borate and molybdate): silver borate glass (AgI)_0.55(Ag₂O:4·B₂O₃)_0.45 has been investigated from 39 to 298 K, and silver molybdate glasses (AgI) _x (Ag₂MoO₄)_1−x , with x = .67 and x = 0.75, from 25 K to T _g (330–350 K). In spite of the very different character of their host matrices, these two families of glasses display a very similar local thermal behaviour around iodine: the mean distance and the coordination number of the short-range I-Ag distribution decrease when the temperature increases. These experimental results can be related to the temperature dependence of the diffusion of the silver ions, giving new elements to better understand the mechanism of ionic conduction.

Acknowledgements

The authors are grateful to C. Armellini for sample preparation and to the staff of the BM29 beamline at ESRF for technical assistance. The financial support by ESRF (Projects HS-1666 and HS-2463) is acknowledged. A.S. acknowledges also the support of the Provincia Autonoma di Trento, through the LOTHEX project at IFN-CNR.