Fig. 3: Ionic conductivity (\({\sigma }_{{EIS}}\)) and phase fraction versus nitrogen doping.

The data show that as the phase fraction of the nitride-hydride grows, so does the \({\sigma }_{{EIS}}\). The \({\sigma }_{{EIS}}\) are offset to show that the values represent the average of the measured conductivities between diffraction experiments. The error bars represent one standard deviation. Notice that after dose 4 and the first diffraction dataset that a large error is present for \({\sigma }_{{EIS}}\) This error disappears when the phase fraction stabilizes sometime after the second diffraction pattern was taken (N4-2). The large change is EIS signal is shown in Supplementary Fig. 14. The next important information in this figure is the drop in conductivity after the 6th dose. Upon the 6th dose of nitrogen the resistance associated with the sample–electrode interface grew dramatically probably a result of delamination. This resulted in the Rs value associated with the bulk conductivity being difficult to measure accurately (see Supplementary Fig. 14); allowing for only the first few datasets to be analysed. EIS results obtained in a separate experiment show that the \({\sigma }_{{EIS}}\) is stable for β-Ca₂NH over long periods (see Supplementary Fig. 16).