Low temperature-densified NASICON-based ceramics promoted by Na2O-Nb2O5-P2O5 glass additive and spark plasma sintering

The effects of spark plasma sintering (SPS) and Na2O-Nb2O5-P2O5 glass additive have been examined for the sintering of Na3Zr2Si2PO12 (NASICON) ceramics. Full densification of NASICON ceramics is achieved at ~1045 °C, which is 200 °C lower than that of typical conventional sintering. The glass addition is demonstrated to markedly promote densification without any negative effects on electrical conductivity. Among all the glass-added samples, the 5 wt% glass-added sample sintered at 1045 °C for 30 min by SPS exhibits the highest ionic conductivity of 1 × 10−3 S cm−1 at 25 °C with the lowest activation energy of 0.32 eV. These properties are almost the same as those of conventional NASICON ceramics. Formation of a trace amount of NaNbO3 as a secondary phase in the glass-added ceramics is due to an insolubility of Nb in the NASICON phase, and has little influence on the electrical conductivity.