X-ray analysis of the structure of Ag-tetraborate glasses (AgI)x (Ag2O•4B2O3)1-x

New X-ray diffraction measurements on (AgI)(x)(Ag2O . 4B(2)O(3))(1-x) glasses with AgI in a concentration range, x, from 0 to 0.55 are presented. The X-ray scattering diagram changes significantly when AgI is added to the tetraborate glass. The pre-peak, located at 1.12 Angstrom(-1) for Ag-tetraborate, moves to 1.0 Angstrom(-1) for x = 0.1 and then shifts continuously until it reaches 0.91 Angstrom(-1) for I = 0.55. At the same time, the :Jeak amplitude increases. The radial electron density distribution curves obtained show that the peak corresponding to the first Ag-I coordination shell increases, and confirm that ordering of AgI units at greater distances is not present in these glasses. The analysis of these new data supports the already proposed structural mechanism for embedding AgI into silver borate glasses: in the Ag-tetraborate, as well as in the Ag-diborate, the AgI-rich regions start to organise to form a network surrounding the borate configurations. X-ray data confirm that, when the AgI content is increased, the borate configurations are separated by greater distances. The position of the smaller first scattering peak corresponds to the distance between the regions filled with borate configurations. (C) 1998 Elsevier Science B.V. All rights reserved.