title: Fast ion conductivity in strained defect-fluorite structure created by ion tracks in Gd2Ti2O7.
abstract: The structure and ion-conducting properties of the defect-fluorite ring structure formed around amorphous ion-tracks by swift heavy ion irradiation of Gd2Ti2O7 pyrochlore are investigated. High angle annular dark field imaging complemented with ion-track molecular dynamics simulations show that the atoms in the ring structure are disordered, and have relatively larger cation-cation interspacing than in the bulk pyrochlore, illustrating the presence of tensile strain in the ring region. Density functional theory calculations show that the non-equilibrium defect-fluorite structure can be stabilized by tensile strain. The pyrochlore to defect-fluorite structure transformation in the ring region is predicted to be induced by recrystallization during a melt-quench process and stabilized by tensile strain. Static pair-potential calculations show that planar tensile strain lowers oxygen vacancy migration barriers in pyrochlores, in agreement with recent studies on fluorite and perovskite materials. In view of these results, it is suggested that strain engineering could be simultaneously used to stabilize the defect-fluorite structure and gain control over its high ion-conducting properties.
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831.
authors.forename: Dilpuneet S
authors.initials: DS
authors.lastname: Aidhy
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831.
authors.forename: Ritesh
authors.initials: R
authors.lastname: Sachan
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831.
authors.forename: Eva
authors.initials: E
authors.lastname: Zarkadoula
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831.
authors.forename: Olli
authors.initials: O
authors.lastname: Pakarinen
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831.
authors.forename: Matthew F
authors.initials: MF
authors.lastname: Chisholm
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831.|Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996.
authors.forename: Yanwen
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831.|Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996.
authors.forename: William J
authors.initials: WJ
authors.lastname: Weber