Co-cation conductivity in solid electrolytes based on AFeO(2) (A=K, Rb, Cs)

The regions of formation of solid solutions and the electroconductivity in systems 0.75(A(1-x)A(x)(1) FeO2) 0.25EO(2) (A, A' = K, Rb, Cs; E = Si, Ti, Ge) are investigated. In the case of A, A' = K, Rb x or Rb, Cs, a continuous series of solid solutions with the fee structure of the gamma-KFeO2 type is formed in both systems. Dependences of conductivity and activation energy on the ratio between the amounts of alkali cations are found to contain extremums, i.e., the polyalkaline effect is observed. The magnitude of this effect in ferrite systems depends less strongly on the unit-cell volume than in aluminate and gallate systems investigated earlier.