Ag 4 I 2 SeO 4 and Ag 3 ITeO 4 – Two New Silver Solid Electrolytes

Two new silver solid electrolytes, Ag 4 I 2 SeO 4 and Ag 3 ITeO 4 , have been synthesized by solid state reactions starting from stoichiometric mixtures of Ag 2 O and AgI with SeO 2 , or TeO 2 , respectively, at elevated oxygen pressures. The new materials have been characterized using powder X‐ray diffraction, differential scanning calorimetry, ionic conductivity measurements and single crystal structure determination. Both compounds, Ag 4 I 2 SeO 4 and Ag 3 ITeO 4 , show an abrupt increase in the ionic conductivity in the temperature range of 50 to 70 °C and 90 to 130 °C, respectively. Ag 4 I 2 SeO 4 has a silver ion conductivity of 1.6 × 10 −3 at 30 °C with an activation energy of 0.22 eV, between 30 and 51 °C. It crystallizes as green crystals in Pna 2 1 with a = 9.3514(1) Å, b = 13.1552(4) Å, c = 7.0886(4) Å, V = 871.80(6) Å 3 and Z = 4. The crystal structure consists of isolated SeO 4 tetrahedra separated by Ag + and I − ions. Ag 3 ITeO 4 crystallizes in P 2 1 / c with a = 19.6597(2) Å, b = 7.1240(4) Å, c = 13.3598(3) Å, β = 97.795(2)°, V = 1853.83(11) Å 3 and Z = 12. The structure consists of $^{1}_{\infty}\rm [TeO_{4/2}O_{2/1}]^{2-}\}$ isopolyanions, extending along the b‐axis. The chains are separated by Ag + and I − ions. Ag 3 ITeO 4 has a silver ion conductivity of 7.4 × 10 −5 Ω −1 cm −1 at 30 °C, with an activation energy of 0.27 eV between 25 and 100 °C.