title: Insights on dramatic radial fluctuations in track formation by energetic ions.
abstract: We report on unexpected dramatic radial variations in ion tracks formed by irradiation with energetic ions (2.3 GeV (208)Pb) at a constant electronic energy-loss (~42 keV/nm) in pyrochlore-structured Gd2TiZrO7. Though previous studies have shown track formation and average track diameter measurements in the Gd2TixZr(1-x)O7 system, the present work clearly reveals the importance of the recrystallization process in ion track formation in this system, which leads to more morphological complexities in tracks than currently accepted behavior. The ion track profile is usually considered to be diametrically uniform for a constant value of electronic energy-loss. This study reveals the diameter variations to be as large as ~40% within an extremely short incremental track length of ~20 nm. Our molecular dynamics simulations show that these fluctuations in diameter of amorphous core and overall track diameter are attributed to the partial substitution of Ti atoms by Zr atoms, which have a large difference in ionic radii, on the B-site in pyrochlore lattice. This random distribution of Ti and Zr atoms leads to a local competition between amorphous phase formation (favored by Ti atoms) and defect-fluorite phase formation (favored by Zr atoms) during the recrystallization process and finally introduces large radial variations in track morphology.
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Ritesh
authors.initials: R
authors.lastname: Sachan
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Eva
authors.initials: E
authors.lastname: Zarkadoula
authors.affiliation: Department of Nuclear Engineering, University of Tennessee, Knoxville, TN, 37996, USA.
authors.forename: Maik
authors.initials: M
authors.lastname: Lang
authors.affiliation: GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstrasse, 1, Darmstadt, 64291, Germany.|Materialwissenschaft, Technische Universität Darmstadt, Darmstadt, 64287, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Trautmann
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.|Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN, 37996, USA.
authors.forename: Yanwen
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Matthew F
authors.initials: MF
authors.lastname: Chisholm
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.|Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN, 37996, USA.
authors.forename: William J
authors.initials: WJ
authors.lastname: Weber