Potassium ion conducting K2 − 2xFe2 − xPxO4 solid electrolytes

Potassium ion conducting solid electrolytes based on potassium monoferrite have been prepared by substituting pentavalent phosphorus cations for Fe 3+ . The highest conductivity of K 2 − 2 x Fe 2 − x P x O 4 is achieved in the range x = 0.05−0.10: 7.1 × 10 −3 S/cm at 300°C and 1.6 × 10 −1 S/cm at 700°C. The rise in the conductivity of KFeO 2 upon phosphorus doping is due to the formation of potassium vacancies.