Anomalous X-ray scattering studies on superionic glassy (As2Se3)-(AgX) systems (X = halides)

Anomalous X-ray scattering experiments for glassy room-temperature superionic conductors (As2Se3)0.4 (AgI)0.6 and (As2Se3)0.4(AgBr)0.6 were performed close to the As, Se, Ag, and Br K edges using a third-generation synchrotron radiation facility, ESRF. The differential structure factors, ΔiS(Q), were obtained from detailed analyses, indicating that ΔAsS(Q) and ΔSeS(Q) of both the glassy superionic semiconductors are similar to those of glassy As2 Se3 except the prepeak in ΔSeS(Q). The ΔAgS(Q) spectrum of (As2Se3)0.4 (AgI)0.6 looks molten salt-like. However, the ΔAg S(Q) of (As2Se3)0.4(AgBr)0.6 glass have quite different features from that of (As2Se3)0.4 (AgI)0.6 glass in the low Q range, and the ΔBrS(Q) has even a pre-shoulder around 13 nm− 1 unlike molten salts. In the differential pair distribution functions Δig(r) obtained from the Fourier transforms of ΔiS(Q), the first peaks of ΔAsg(r) and ΔSeg(r) show no correlation with those of ΔAgg(r) and ΔBrg(r), and vice versa. From these results, it can be concluded that a pseudo-binary mixture of the As2Se3 network matrix and AgX-related ionic conduction pathways is a good structural model for these superionic glasses. Differences between the AgBr- and AgI mixtures were found in the second-neighbor structures around the Ag atoms, which may reflect those in the crystal structures of the AgX salts.