Figure shows the ionic conductivities obtained from EIS measurements for all Na₁₊ₓZnₓAl₁₋ₓCl₄ nominal compositions under different applied pressures. The same data are also shown on a logarithmic scale in Figure . For x = 0, the pure NAC composition exhibits an ionic conductivity of 1.5 × 10⁻⁶ S/cm at 2 MPa. Increasing the pressure to 200 MPa makes little difference, i.e. the conductivity only reaches 3.3 × 10⁻⁶ S/cm at 200 MPa. As x increases, the ionic conductivity shows an upward trend, reaching a maximum value of 1.5 × 10⁻⁵ S/cm at 35 MPa for Zn content in the range of 0.5 ≤ x ≤ 0.625.