Effect of Water Incorporation on the Ionic Conduction Properties of the Solid Electrolyte Material RbTiO.(HO)

Previous work has demonstrated the accumulation of negative charges on the anode side of the ion conductor Rb2Ti2O5 when placed under voltage between two metallic electrodes. The nature of these accumulated species and of the conducting ions is investigated by a combination of thermogravimetric analysis (TGA), Xray diffraction, dielectric response measurements, charge distribution, IR absorption spectroscopy and nuclear magnetic resonance (NMR) measurements. TGA shows that the as-grown samples have incorporated a considerable amount of water (up to 0.35 H2O per unit cell) that is eliminated at two different temperature thresholds. However, no significant variation of the lattice parameters is observed by X-Ray diffraction. A strong dependence of the dielectric properties and of the accumulated charge density on the water content is demonstrated. All the results point towards a mechanism of proton and hydroxide conduction associated with a change of valence for titanium.