Hydrogen ion conductivity in 2 and 10%Al-substituted SrTiO3 was investigated by transport number measurements using the concentration cell/emf method in wet atmospheres as a function of pO2 (10-20 to 1atm) at 350 to 1000C. Earlier indications of apparent negative charge transport by H under reducing conditions and high temperatures were confirmed. By the present measurements, possible artefacts from the type of acceptor-dopant, gas buffer, electrode material, and porosity of the sample appeared to be ruled out. Electrochemical pumping experiments with gas chromatography were inconclusive with respect to hydride ion transport. Thermogravimetry as a function of H activity did not show evidence of hydride ion incorporation, but indicated uptake of neutral H under reducing conditions and high temperatures. Quantum molecular dynamics simulations indicated the existence of defect species or clusters that may be reminiscent of interstitial H with a tendency to associate with effective negative charge, e.g., on neighbouring Ti ions, under simulated reducing conditions.

Proton and Apparent Hydride Ion Conduction in Al-Substituted SrTiO3. M.Widerøe, W.Münch, Y.Larring, T.Norby: Solid State Ionics, 2002, 154-155, 669-77