Superionic Ag Conductor Ag(CO)I.

A new superionic Ag conductor with a nominal composition Ag(CO)I (11AgI-3AgCO) was found in the AgI-AgCO system. The conductor, which was formed at temperatures from 100 to 170 °C, is a metastable phase that gradually decomposes into AgI and Ag(CO)I over a period of a few weeks at room temperature (RT). A Ag ionic conductivity of 0.16 S/cm was measured at RT, and an activation energy of 0.33 eV was evaluated in the temperature range from -9 to 19 °C. Single-crystal X-ray analysis revealed that Ag(CO)I crystallized in a rhombohedral unit cell with hexagonal parameters of = 15.8831(6) Å and = 30.0730(13) Å at -183 °C and space group 3. The Ag atoms were distributed over 53 sites in the asymmetry unit, with a maximum occupancy of 0.33(8). The continuous distribution of the partially occupied Ag sites was associated with the conduction paths of the Ag ions in the structure.