Improvement of ionic conductivity and densification of Na3Zr2Si2PO12 solid electrolyte rapidly prepared by microwave sintering

Na3Zr2Si2PO12 (labeled as NZSP) material is one of the most promising solid-state electrolytes for solid Na+ batteries. In this paper, the NZSP electrolytes were prepared by the microwave-assisted solid-phase reaction method, and the effects of different sintering temperatures (1050 °C–1150 °C) on phase composition, microstructure, densification, and ionic conductivity of NZSP samples were probed. XRD results demonstrated the NZSP phase could be formed by using microwave sintering at 1050 °C for 2 h. With the increase of sintering temperature, the density and the room-temperature ionic conductivity of the NZSP samples were gradually improved. After microwave sintering at 1125 °C, the NZSP electrolyte with the room-temperature ionic conductivity of 5.26 × 10−4 S/cm was achieved. Besides, the influences of sintering aid NaF with different contents (y wt%) on the densification and ionic conductivity of NZSP were also studied. It was found that the addition of NaF not only increased the density but also improved the ionic conductivity of NZSP samples. The NZSP ceramics with 0.2 wt% NaF additive sintered at 1125 °C showed a relatively high room-temperature ionic conductivity of 6.02 × 10−4 S/cm. Moreover, the activation energy was evaluated by the Arrhenius equation. The Arrhenius plot revealed the specimen with 0.2 wt% NaF exhibited the lowest activation energy of 0.29 eV.