Electrochemical Properties of Superionic Conductors CsAg4Br3 –хI2 +х

Solid solutions CsAg 4 Br 3 – х I 2 + х ( x = 0.38; 0.50; 0.68) are prepared by solid-state synthesis; the single phase of the products is confirmed using the methods of X-ray diffraction and differential scanning calorimetry. The studies of electrotransport characteristics of CsAg 4 Br 3 – х I 2 + х involve measuring the ionic conductivity by the four-probe method in the temperature interval from –50 to +120°C and estimating its electronic component by the Hebb–Wagner method. It is shown that in the studied interval of compositions, the ionic conductivity of CsAg 4 Br 3 – х I 2 + х solid solutions is practically independent of x, approaching the conductivity of the well-known superionic conductor RbAg 4 I 5 . The activation energy of conduction is found to be about 10 kJ mol –1 for all compounds studied. The oxidation potential determined by the method of stepwise polarization for CsAg 4 Br 3 – х I 2 + х solid solutions is considerably higher as compared with RbAg 4 I 5 , being in the range of 0.75–0.78 V (vs. Ag 0 /Ag + ). The high electrochemical characteristics of CsAg 4 Br 3 – х I 2 + х (0.38 ≤ x ≤ 0.63) and the absence of polymorphic transitions in the considered interval from –160°С to the melting point (175–178°С) make these materials promising for the use in electrochemical devices, especially in low-temperature applications.