To investigate the effect of the an

To investigate the effect of the annealing step on electrochemical performance, a post heat treatment was performed on cold sintered pellets during 10 h at 1000℃, 1100℃ and 1200℃. Results presented in Fig. 11A show that the increase of the annealing temperature is followed by an enhancement of the conductivity level from 3.4 10−3 S. cm−1 at 1000℃ to 2.05 10−2 S. cm−1 at 1100℃ reaching a maximum of 4.10−2 S. cm-1 at 1200℃ with a relative density of 94 %. The differences in conductivity seem to be more important at the intermediate temperatures around 300℃ and the decrease of the total conductivity is mostly due to the grain boundary component (Fig. 11B). The microstructure systematic trend of the different specimens, illustrated in Fig. 12, shows a denser microstructure with more interconnected particles and lower porosity, with simultaneous increase of particle size by increasing the annealing temperature.