Characterization of the intermediate-range order in new superionic conducting AgI-Ag₂S-AgPO₃ glasses by neutron diffraction

Superionic conducting glasses are of considerable technological interest because of their use in batteries, sensors, and displays. We have investigated the new ternary systems AgI-Ag₂S-AgPO₃ where the ratio AgI:Ag₂S is 1:1. The system (AgI)_x(Ag₂S)_x(AgPO₃)_1-2x, for a AgI+Ag₂S fraction less than 82 mol%, yields glasses. We have used a neutron-diffraction technique to obtain the total scattering structure factor S(Q) of this system at room temperature by using the HIT spectrometer at the High Energy Accelerator (KEK), Tsukuba, Japan. As for AgI-AgPO₃ glasses, S(Q) shows a peak at anomalously low Q in the range from 0.6 to 0.9 Å^-1. This peak is not observed in the corresponding glass Ag₂S-AgPO₃ or pure AgPO₃. The peak depends strongly on the dopant salt. Its intensity increases as the amount of (AgI+ Ag₂S) increases and its position shifts to lower Q, while the number density of the glasses decreases with x. This peak can be associated with an intermediate structure of particles lying inside a continuous host with the characteristic length between 5 and 10 Å [1].