Controlled synthesis and characterization of sodium titanate composites Na2Ti3O7/Na2Ti6O13

Sodium titanates mixtures (Na2Ti3O7–Na2Ti6O13) were directly prepared via a sol–gel reaction allowing the production of different mass composition ceramics. A semi-quantitative method based on XRD analysis was proposed to determine the real ratio between Na2Ti3O7 and Na2Ti6O13 obtained after heat treatment.The electrical properties of each ceramic composite were investigated under air, argon and oxygen by electrochemical impedance spectroscopy. These electrical studies show that rich Na2Ti3O7 mixtures have conductivities close to pure Na2Ti3O7 and poor Na2Ti3O7 mixtures have conductivities close to Na2Ti6O13.This study underlines a percolation threshold which can be observed between 20 and 35 wt.% of Na2Ti3O7. Considering the higher conductivity of Na2Ti3O7 in comparison to the Na2Ti6O13 one, the electrical pathways exclusively follow the more favourable material when the percolation limit is reached.