Solid potassium-cation-conducting electrolytes in the systems K2−2x Fe2−x A x O4 (A = Nb, Ta)

Abstract

Highly conductive potassium-cation solid electrolytes based on potassium monoferrite with cations Nb5+ and Ta5+ partially replacing cations Fe3+ are synthesized and studied. Both additives cause a sharp increase in the conductivity of KFeO2 at temperature below ∼700°C. The two solid electrolytes have similar electric characteristics, which is apparently associated with the close sizes of the doping cations. The increase in the conductivity of potassium monoferrite with the introduction of dopants studied is associated with the formation of potassium vacancies at the substitution Fe3+ → Nb5+ (Ta5+) + 2 V′c and also with the elimination of a phase transition typical of pure KFeO2.