A high Mg2+ ion-conducting phosphate-based solid electrolyte of solid-solution form was prepared by substituting tetravalent Zr4+ for pentavalent Nb5+. The activation energy for Mg2+ ion migration became considerably lower when compared with that of Zr4MgP6O24, and an appreciable enhancement of the Mg2+ ionic conductivity was observed. The successful formation of the solid solution resulted in a statistical distribution of mobile Mg2+ ions in 3 sites which were occupied by mobile Mg2+ and contributed greatly to permitting smooth Mg2+ ion migration in the solid solution.

Divalent Magnesium Ionic Conduction in Mg(Zr,Nb)4P6O24 Solid Solutions. N.Imanaka, Y.Okazaki, G.Adachi: Electrochemical and Solid State Letters, 2000, 3[7], 327-9