Screening of Sintering Aids for Oxide Ceramics: A Case of NASICON Electrolyte

In this work, an efficient screening method to select appropriate sintering aids for a wide range of oxide material systems is developed. Consequently, Na₂ B₄ O₇ , NaF, and CuO are selected as sintering aids for sodium super ionic conductor (NASICON)-type Na₃ Zr₂ Si₂ PO₁₂ ceramic to verify the feasibility of the as-proposed method. As evidenced by the results, the sinterability and densification of ceramic matrix are apparently improved. Specifically, Na₃ Zr₂ Si₂ PO₁₂ -7%Na₂ B₄ O₇ , Na₃ Zr₂ Si₂ PO₁₂ -3%NaF, and Na₃ Zr₂ Si₂ PO₁₂ -3%CuO endow much higher room temperature ionic conductivity of 1.03 × 10^-3 , 1.61 × 10^-3 , and 1.63 × 10^-3  S cm^-1 , respectively, in comparison with the pristine (7.23 × 10^-4  S cm^-1 ). The underlying mechanism for the enhanced performance is also discussed. The symmetric sodium cells assembled with sintering aids modified Na₃ Zr₂ Si₂ PO₁₂ ceramic electrolyte exhibit ultra-stable metallic Na plating/stripping at room temperature. Moreover, solid-state sodium batteries paired with Na₃ V_1.5 Cr_0.5 (PO₄ )₃ cathode active material and modified Na₃ Zr₂ Si₂ PO₁₂ ceramic electrolyte demonstrate superior cycling stability and excellent rate capability. Furthermore, an as-developed strategy can be universally extended to synthesize high-performance oxide ceramics.