Mechano-chemical synthesis of amorphous solids in the system AgI–Ag2PO3.5 and their silver ion-conducting properties

Amorphous fine powders in the system AgI–Ag2PO3.5 were obtained over a wide composition range of 20–70 mol% AgI by a high-energy ball-milling process. While an amorphous sample was not obtained of the composition 80AgI · 20Ag2PO3.5 (mol%) by the ball-milling process, the amorphous sample-forming region by the high-energy ball-milling process was very similar to the glass-forming region by a conventional melt-quenching method. The 60AgI · 40Ag2PO3.5 (mol%) composition, at which an amorphous sample was obtained by ball milling to 48 h, was the most easily amorphous-forming composition in the system AgI–Ag2PO3.5. Ball-milled samples showed high ion conductivities at room temperature. The σ298 of the 60AgI·40Ag2PO3.5 sample changed with the ball-milling time. The σ298 steeply increased with an increase in the milling time and showed a maximum of 7.3×10−1 Sm−1 at around 20 h. It was noted that the maximum conductivity was higher than the conductivity of the melt-quenched glass with the same chemical composition. The σ298 of the samples ball-milled for longer than 30 h decreased with an increase in the milling time, and had a similar value as that of a melt-quenched glass.