title: Fast oxygen exchange and diffusion kinetics of grain boundaries in Sr-doped LaMnO3 thin films.
abstract: In this study, the contribution of grain boundaries to the oxygen reduction and diffusion kinetics of La0.8Sr0.2MnO3 (LSM) thin films is investigated. Polycrystalline LSM thin films with columnar grains of different grain sizes as well as epitaxial thin films were prepared by pulsed laser deposition. (18)O tracer exchange experiments were performed at temperatures from 570 °C to 810 °C and subsequently analyzed by secondary ion mass spectrometry (SIMS). The isotope concentration depth profiles of polycrystalline films clearly indicate contributions from diffusion and surface exchange in grains as well as in grain boundaries. Measured depth profiles were analyzed by finite element modeling and revealed the diffusion coefficients D and oxygen exchange coefficients k of both the grain bulk and grain boundaries. Values obtained for grain boundaries (Dgb and kgb) are almost three orders of magnitude higher than those of the grains (Dg and kg). Hence, grain boundaries may not only facilitate fast oxygen diffusion but also fast oxygen exchange kinetics. Variation of the A-site stoichiometry ((La0.8Sr0.2)0.95MnO3) did not lead to large changes of the kinetic parameters. Properties found for epitaxial layers without grain boundaries (Db and kb) are close to those of the grains in polycrystalline layers.
authors.affiliation: Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9, Vienna A-1060, Austria. J.Fleig@tuwien.ac.at.
authors.forename: Edvinas
authors.initials: E
authors.lastname: Navickas
authors.forename: Tobias M
authors.initials: TM
authors.lastname: Huber
authors.forename: Yan
authors.initials: Y
authors.lastname: Chen
authors.forename: Walid
authors.initials: W
authors.lastname: Hetaba
authors.forename: Gerald
authors.initials: G
authors.lastname: Holzlechner
authors.forename: Ghislain
authors.initials: G
authors.lastname: Rupp
authors.forename: Michael
authors.initials: M
authors.lastname: Stöger-Pollach
authors.forename: Gernot
authors.initials: G
authors.lastname: Friedbacher
authors.forename: Herbert
authors.initials: H
authors.lastname: Hutter
authors.forename: Bilge
authors.initials: B
authors.lastname: Yildiz
authors.forename: Jürgen
authors.initials: J
authors.lastname: Fleig