The ionic conductivities vary strongly upon substitution with room-temperature values ranging from 0.088 to 5.0 S/m as determined by impedance spectroscopy. The respective Arrhenius behavior for Ag8SiSe6, Ag8GeSe6 and Ag8SnSe6 reveals significant changes to the activation barrier and, with that, the temperature dependence of ionic transport (Figure ). Here, Ag8GeSe6 exhibits the lowest activation barrier of 0.05 eV while both Ag8SiSe6 and Ag8SnSe6