Influence of temperature on the local structure around iodine in fast-ion-conducting Agl:Ag2MoO4 glasses

Extended x-ray absorption fine structure (EXAFS) measurements have been performed at the K edge of iodine in (AgI)(1-y)(Ag2MoO4)(y) glasses, with y = 0.25 and 0.33, as a function of temperature from 25 K to the glass transition temperature T-g similar or equal to 323 K. EXAFS monitors the short-range component of the I - Ag distance distribution. At 25 K, iodine coordinates to about four silver ions, at an average distance about 0.06 angstrom larger than in beta-AgI. As temperature increases, EXAFS monitors a progressive depletion of the short-range distribution, due to transitions of Ag ions into a long-range component. Coordination number and mean value of the short-range I - Ag distribution decrease while temperature is increasing. EXAFS results give information on the local modifications around iodine due to the ionic diffusivity.