Divalent magnesium ionic conduction in Mg1-2x(Zr1-xNbx)(4)P6O24 (x=0-0.4) solid solutions

A high Mg2+ ion-conducting phosphate-based solid electrolyte with a solid s olution form was synthesized by substituting the tetravalent Zr4+ site in M gZr4P6O24 for a pentavalent Nb5+. Because of the replacement, the activatio n energy for Mg2+ ion migration became considerably low compared with that for the mother phase of MgZr4P6O24 and an appreciable enhancement of Mg2+ i on conductivity was observed especially in a relatively low-temperature reg ion. The Zr4+ site substitution in MgZr4P6O24 for Nb5+ makes for a superior effect on the stabilization of the high-temperature phase of MgZr4P6O24. A successful formation of the above mentioned solid solution results in the statistical distribution of mobile Mg2+ ion in three sites occupied by mobi le Mg2+ and contributes greatly to making a smooth Mg2+ ion migration in th e solid solution. (C) 2000 The Electrochemical Society. S1099-0062(00)03-08 6-8. All rights reserved.