Abstract

The divalent Mg²⁺ ion conducting solid electrolyte was synthesized with a composite form by intentionally changing the starting material mixing ratio to the nonstoichiometric region. By such a preparation technique, spontaneous and microscopic dispersion of the secondary Zr₂O(PO₄)₂ phase was successfully realized and the Mg²⁺ ion conductivity was considerably enhanced by dispersing the secondary phase, showing the highest conductivity among the Mg²⁺ ionic conducting solid electrolytes reported. The Mg²⁺ migration in the composite solid was clearly demonstrated by dc electrolysis and the Mg²⁺ ion transference number was precisely determined to be unity by a modified Tubandt method. The development of pure Mg²⁺ ion conducting phosphate based solid electrolytes with high stability and considerably high ionic conductivity contributes greatly to opening a new door for the application of advanced materials such as rechargeable batteries and other specific sensor elements.