Atomic-scale picture of the ion conduction mechanism in a tetrahedral network of lanthanum barium gallate

Combined experimental study of impedance spectroscopy, neutron powder diffraction, and quasielastic neutron scattering was performed to shed light onto the atomic-scale ion migration processes of protons and oxide ions in La_0.8Ba_1.2GaO_3.9. This material consists of tetrahedral GaO₄units, which are rather flexible, and rocking motion of these units promotes the ionic migration process. The oxide ion (vacancy) conduction takes place on channels along the c axis, involving a single elementary step, which occurs between adjacent tetrahedra (intertetrahedra jump). The proton conduction mechanism consists of intratetrahedron and intertetrahedra elementary processes. The intratetrahedron proton transport along the c axis is the rate-limiting process, with activation energy of 0.44 eV. The intertetrahedra proton transport has the activation energy of 0.068 eV.