This study focused on the effect of Zr-inclusion on Na[Formula: see text] conduction properties of the newly developed glass–ceramic solid solutions of Na5FeSi4O[Formula: see text] and Na4ZrSi4O[Formula: see text]. We experimentally confirmed formation of an all proportional solid solution in the range of [Formula: see text]= 0 and 1.0 with the composition Na[Formula: see text]Fe[Formula: see text]Zr[Formula: see text]Si4O[Formula: see text]. Glass–ceramic with a fast Na[Formula: see text]-conducting Na5YSi4O[Formula: see text]-type single phase was obtained in all the solid solutions. The conduction properties of the glass–ceramics were improved with increasing content of Zr, and Na4ZrSi4O[Formula: see text] was the most conductive glass–ceramic. The ionic conductivities were as high as 1.9 × 10[Formula: see text] S cm[Formula: see text] and 9.3 × 10[Formula: see text] S cm[Formula: see text] at temperatures of 25[Formula: see text]C and 300 [Formula: see text]C, respectively. The improved conductivity was attributed to the expansion of the conduction path by larger Zr ions replacing FeO6 octahedra.
Microstructural effects on sodium ion conduction properties of grains and grain boundaries of Na5YSi4O12-type silicophosphate glass-ceramics
