New potassium solid electrolytes in the systems K 3-2x M x PO 4 (M = Mg, Zn) were synthesized and studied. The introduction of Mg2+ and Zn2+ cations leads to sharp increasing of K 3 PO 4 conductivity due to potassium vacancies formation and stabilization of high temperature cubic modification of orthophosphate. Maximum conductivity is observed at x ? 0.15–0.25 and is equal to (6–8)·10-2 S·cm-1 at 400°C, higher than 10-1 S·cm-1 at 700°C.
