Solid electrolytes in the binary system RbNO3–RbNO2

Conductivity and thermodynamic properties of solid solutions (1−x)RbNO3–xRbNO2 were investigated over entire concentration range of 0 < x < 1. As shown by differential thermal analysis and conductivity measurements, the introduction of a small concentration of nitrite into rubidium nitrate leads to an decrease in the temperature of phase transitions IV↔III and III↔II, so that highly conducting phase III becomes stable at low temperatures. The introduction of smaller NO2− anions results in the increase in the conductivity of the RbNO3-III phase, the activation energy and a pre-exponential factor of conductivity decrease with the doping and III–IV transition becomes diffusive. A possible reason of these effects is a strong influence of nitrite ions to the orientational disorder of the anionic sublattice of RbNO3.