Different samples were obtained by adding 5, 10 and 20 wt% of water, before being cold sintered under 375 MPa at 180℃ during 30 min and finally heated at 1200℃ during 10 h. The electrochemical impedance spectra were recorded between 150℃ and 800℃ under dry atmosphere. For example, Fig. 1 compares the Nyquist plots obtained at two different temperatures (158℃ and 548 ℃) for the sample prepared with 5 wt% of water.