Cold sintering of Na3Zr2Si2PO12 solid electrolyte: Effect of mechanical pressing and post-annealing

We investigated the effect of mechanical pressing and post-annealing on aqueous cold-sintered Na₃Zr₂Si₂PO₁₂ (NZSP) solid electrolyte, comparing the results with conventionally sintered NZSP. Various physical, microscopic and spectroscopic techniques, including Archimedes, Impedance spectroscopy, XRD and SEM, were used to investigate the properties of the cold-sintered NZSP solid electrolyte. X-ray diffraction confirmed the retention of the NaSICON phase in cold-sintered NZSP, with the secondary m -ZrO₂ peaks becoming prominent. Scanning electron microscopy revealed that post-annealing improved the ceramic's morphology, showing grain formation and inter-granular porosity remained. With an ionic conductivity of 2.45 × 10 ^⁻ ⁵ S/cm at 25 °C, NZSP ceramics post-annealed at 400 °C showed no susceptibility to mechanical pressing. Conductivity increased tenfold after post-annealing at 800 °C, reaching 1.43 × 10 ^- ⁴ S/cm.