Divalent Magnesium Ionic Conduction in Mg_(1-2x)(Zr_(1-x)Nb_x)_4P_6O_(24) (x = 0-0.4) Solid Solutions

摘要

A high Mg~(2+) ion-conducting phosphate-based solid electrolyte with a solid solution form was synthesized by substituting the tetravalent Zr~(4+) site in MgZr_4P_6O_(24) for a pentavalent Nb~(5+). Because of the replacement, the activation energy for Mg~(2+) ion migration became considerably low compared with that for the mother phase of MgZr_4P_6O_(24) and an appreciable enhancement of Mg~(2+) ion conductivity was observed especially in a relatively low-temperature region. The Zr~(4+) site substitution in MgZr_4P_6O_(24) for Nb~(5+) makes for a superior effect on the stabilization of the high-temperature phase of MgZr_4P_6O_(24). A successful formation of the above mentioned solid solution results in the statistical distribution of mobile Mg~(2+) ion in three sites occupied by mobile Mg~(2+) and contributes greatly to making a smooth Mg~(2+) ion migration in the solid solution.