Structure of glassy AsTe: the effect of adding a small quantity of Cu or Ag

The structure of the glasses Cu0.1AsTe and Ag0.1AsTe is studied by using th e method of isotopic substitution in neutron diffraction. It is found that the addition of metal atoms M(=Cu orAg) does not significantly affect the s tructure of glassy AsTe on either the short- or intermediate-range length s cales. Cu and Ag both take coordination numbers in excess of four in an As- Te network that is compact by comparison with its As-S and As-Se counterpar ts. In high-M-content M-As-Te glasses, Cu and Ag again take coordination nu mbers greater than four and the absence of significant ionic conductivity f or the Ag-based materials is attributed to a compact As-Te network that res tricts pathways along which silver ions can move.