EXAFS studies of the local thermal expansion in borate glasses

Temperature-dependent EXAFS measurements have recently been made on the silver borate glass [Ag2O·4B2O3], and the superionic AgI-doped glass [AgI]0.75[3Ag2O·1B2O3]0.25. The Ag–O co-ordination has been studied in the first sample, the I–Ag in the second one. In both cases a significant reduction of the first shell inter-atomic distance has been observed as temperature increases from 15 to 300 K. Here a detailed analysis of the EXAFS results for the AgI-doped glass is presented. The distributions of first shell I–Ag distances reconstructed from EXAFS for the glass and c-AgI, and their leading statistical parameters, are compared and critically discussed. The local negative expansion in the glass is partially attributed to the relaxation of the a-AgI network within the host binary matrix.