Figure 5.

(a) DC conductivity at room temperature as a function of relative humidity (RH), (b) recovery experiment: 1st measurement—conductivity spectrum at RH = 49% (ambient), 2nd measurement—conductivity spectrum at RH = 95% for 2 h and 3rd measurement—conductivity spectrum at RH ≈ 10% recorded 12 h after exposure to high humidity and (c) time-dependent conductivity at RH = 84% and 95% for glass-ceramics prepared at 450 °C for 24 h. Note that the strong electrode polarization effect in the conductivity spectrum measured at RH = 95% (Figure b) is due to proton conductivity, i.e., blocking of protons at the surface of the electrode.