Mechanochemically synthesized Ag2S–Sb2S3 amorphous fast ionic conductors

The mechanochemical synthesis of (Ag2S)x–(Sb2S3)1−x amorphous fast ion conductors (a-FICs) and their structural, thermal and electrical characterizations are investigated. It is found that after ∼10 h of ball-milling, the composition 0.85Ag2S–Sb2S3 becomes amorphous and attains a conductivity of ∼6 × 10−3 Ω−1 cm−1 at 25 °C which is three times greater than that of the analogous melt-quenched glass. These a-FICs are found to be predominantly ionic in nature and stable under battery conditions. By examining conductivity (σ) versus composition (x), it is concluded that the sharp rise in the conductivity with the dopant Ag2S content is largely due to a significant increase in the mobility (μ) of Ag+ ions. These results imply that the role of salts (such as Ag2S) is not so much to provide free (Ag+) ions for conduction but to modify the glass structure in a manner that favours fast ion transport. It is believed that these findings will guide the development of various models to relate ion transport with glass structure.