In-situ investigation of oxygen diffusion in Sr, Mg-doped LaGaO3 superionic conductors with a simultaneously applied electric field

In-situ neutron powder diffraction investigations of the oxygen super-ionic conductors La0.9Sr0.1Ga0.8Mg0.2O2.85 and La0.8Sr0.2Ga0.8Mg0.2O2.80 were performed at 1460 K with and without an applied electric field (U = 3 V DC) resulting in lasting ionic currents of 180-270 mA. At this temperature both samples adopt the cubic perovskite structure (Pm3m). Field-induced structural changes are evidenced by anharmonic terms in the Debye-Waller factors of oxygen only for the first sample. The corresponding probability density function maps indicate curved diffusion pathways around the Ga atoms shifted further into the direction of an octahedral void with applied field. In addition, double maxima appear in the direction of the Ga-O bond which are more prominent in the second sample. A tentative explanation of the observed phenomena is given in terms of long range ordering of the corresponding potential minima and residual short range order clusters persisting at high temperatures.