Local Structural Modifications versus Transport Properties in AgI-Doped Silver–Borate Glasses: A Detailed X-ray Absorption Investigation

The short-range order around iodine in AgI-doped silver–borate glasses (AgI)x(Ag2O·nB2O3)1–x has been studied as a function of both AgI content and temperature by means of extended X-ray absorption fine structure (EXAFS) spectroscopy in order to investigate the relationship between local structure and conductivity. An interpretation of the EXAFS cumulants specifically tailored for ion conducting glasses has been employed. The reduction of the number of Ag ions coordinated to I and the modifications of the I–Ag distance distribution probed by EXAFS when ionic conductivity increases, by temperature or AgI content, are strictly correlated with the progressive growth of silver ions undergoing diffusion. The results are discussed in the framework of the bond valence model and mixed iodine/oxygen coordination of silver ions.