Synthesis of Solid Electrolyte Nasicon by Solid State Reaction

Solid electrolyte nasicon was synthesized by the optimized solid state reaction minimizing the volume fraction of secondary ZrO₂ and glassy phases. To compensate for the evaporation of Na and P during heat-treatment, excess Na and P were added to the starting composition Na 1+x Zr₂Si x P 3-x O 12 (x=2.1). Phase pure nasicon comparable in volume fraction to the one obtained from sol-gel process were synthesized after the reaction at 1100~1150℃, P O2 = 0.1-0.15 atm for 24 hrs. The volume fraction of ZrO₂ increased with the heat-treatment time due to the decomposition of nasicon phase and that of glassy phase increased as partial oxygen pressure decreased. The synthesized nasicon showed a good electrical conductivity of~1×10 -2 (Ω·cm) -1 at 350℃.