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, Na₂B₄O₇, NaF, and CuO are selected as sintering aids for sodium super ionic conductor (NASICON)-type Na₃Zr₂Si₂PO₁₂ 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, Na₃Zr₂Si₂PO₁₂-7%Na₂B₄O₇, Na₃Zr₂Si₂PO₁₂-3%NaF, and Na₃Zr₂Si₂PO₁₂-3%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 Na₃Zr₂Si₂PO₁₂ ceramic electrolyte exhibit ultra-stable metallic Na plating/stripping at room temperature. Moreover, solid-state sodium batteries paired with Na₃V_1.5Cr_0.5(PO₄)₃ cathode active material and modified Na₃Zr₂Si₂PO₁₂ 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.