Fig. 5: Optimization of ionic conductivity via Sc doping.

a XRD patterns. The peaks between 18° and 20° are highlighted to show the change in crystal symmetry. b Nyquist plots obtained from EIS at room temperature (~25 °C). Indium metal was used as blocking electrodes for Na3HfZrSi2PO12, whereas Na metal was used as the electrodes for Na3.2Hf0.8Sc0.2ZrSi2PO12 and Na3.4Hf0.6Sc0.4ZrSi2PO12. c Na stripping and plating tests in a temperature chamber at 25 °C at various current rates of a Na|Na3.4Hf0.6Sc0.4ZrSi2PO12 | Na symmetric cell.