Co-cation Conduction in Solid Solutions (K_{1 − x}Rb_x)₄P₂O₇–M₂P₂O₇ (M = Ca, Sr, Cd, Ba)

Solid solutions of the structure γ-K₄P₂O₇, which have the composition (K_{1 − x}Rb_x)_3.8M_0.1P₂O₇(M = Ca, Sr, Cd, Ba) and (K_{1 − x}Rb_x)_{4 − 2y}Ca_yP₂O₇(y= 0.025–0.20), are synthesized. The solutions' electroconductivity is studied in the temperature range 400–600°C. The concentration dependences of the conductivity and the activation energy for conduction have extremums at x≈ 0.6, which points to the polyalkaline effect. The effect increases with decreasing radius of cation M²⁺and with increasing concentration of calcium cations, which is explained by an increased energy nonequivalence of positions in the cation sublattice accessible to alkali ions.