Effect of water incorporation on the ionic conduction properties of the solid electrolyte material Rb2Ti2O5.(H2O)x

• Published in: Solid state ionics Vol. 364; p. 1
• Main Authors: de Sousa Coutinho, Sofia, Bérardan, David, Lang, Guillaume, Federicci, Rémi, Giura, Paola, Beneut, Keevin, Dragoe, Nita, Holé, Stéphane, Leridon, Brigitte
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.06.2021; Elsevier BV
• Subjects: Charge density; Charge distribution; Conduction; Conductors; Dielectric properties; Dielectric strength; Dielectrics; Diffraction; Electrolytes; Infrared spectroscopy; Ions; Lattice parameters; Moisture content; NMR; Nuclear magnetic resonance; Potassium dititanate; Rubidium dititanate; Solid electrolyte; Solid electrolytes; Supercapacitor material; Superionic conductor; Thermogravimetric analysis; Titanium; Unit cell; Virtual cathode; X-ray diffraction; 99-00; Supercapacitor material; 00-01; Solid electrolyte; Rubidium dititanate; Potassium dititanate; Virtual cathode; Superionic conductor
• ISSN: 0167-2738; 1872-7689
• DOI: 10.1016/j.ssi.2021.115630

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. •Equivalent permittivity and conductivity of (Rb2Ti2O5)H2Ox ceramics are found to be highly dependent on the water content•Accumulated negative charge decrease with the rise of temperature following the same trend as water losses measured by TGA•IR absorption measurements confirm the presence of molecular and dissociated water in as grown samples•NMR measurements enable to exclude rubidium ions as the diffusive species; negative ionic carriers are inferred to be hydroxide ions•Ionic carriers are provided by water dissociation and incorporated water favors ion conduction through a Grotthuss mechanism