Sol–gel synthesis of NASICON discs from aqueous solution

Abstract

Sodium superionic conductor (NASICON: Na _1+x Zr ₂ Si _x P _3-x O ₁₂ ) discs of high density and relatively high purity can be easily synthesized with good reproducibility by a sol–gel method using a mixed solution of inorganic materials, by evaporation, calcination, and sintering. The densities and ionic conductivities of the NASICON discs were largely dependent on the calcination and sintering conditions, the optimum temperatures of which were found to be 750 °C (1 h) and 1000 °C (6 h), respectively. It was also found that high-density and relatively high-purity NASICON discs could be derived more easily by controlling the pH of the sol in the first step to ca. 3.0.