Low temperature sintering of Na1 + xZr2SixP3 − xO12 by the addition of Na3BO3

Na_{1 + x}Zr₂Si_xP_{3 − x}O₁₂ (NASICON)-based solid electrolytes were prepared by liquid phase sintering with a Na₃BO₃ additive to lower the NASICON sintering temperature. NASICON was sintered at 700 °C with 9.1 wt% Na₃BO₃. The obtained NASICON ceramic exhibited high room-temperature conductivity of 1 × 10^{− 4} S cm^{− 1}, which were three orders of magnitude higher than that of a Na₃BO₃-free sample. SEM observation of this ceramic revealed that neck growth among NASICON grains proceeded reasonably and that sodium borates segregated in particulate form without full penetration to NASICON grain boundaries. This characteristic microstructure is expected to contribute to the high conductivity of the NASICON-Na₃BO₃ ceramic.