Title: Response of Gd₂Ti₂O₇ and La₂Ti₂O₇ to swift-heavy ion irradiation and annealing

Abstract

Swift heavy ion (2 GeV ¹⁸¹Ta) irradiation-induced amorphization and temperature-induced recrystallization of cubic pyrochlore Gd₂Ti₂O₇ (Fd3¯m) are compared with the response of a compositionally-similar material with a monoclinic-layered perovskite-type structure, La₂Ti₂O₇ (P2₁). The averaged electronic energy loss, dE/dx, was 37 keV/nm and 35 keV/nm in Gd₂Ti₂O₇ and La₂Ti₂O₇, respectively. Systematic analysis of the structural modifications was completed using transmission electron microscopy, synchrotron X-ray diffraction, Raman spectroscopy, and small-angle X-ray scattering. Increasing ion-induced amorphization with increasing ion fluence was evident in the X-ray diffraction patterns of both compositions by a reduction in the intensity of the diffraction maxima concurrent with the growth in intensity of a broad diffuse scattering halo. Transmission electron microscopy analysis showed complete amorphization within ion tracks (diameter: ~10 nm) for the perovskite-type material; whereas a concentric, core–shell morphology was evident in the ion tracks of the pyrochlore, with an outer shell of disordered yet still crystalline material with the fluorite structure surrounding an amorphous track core (diameter: ~9 nm). The radiation response of both titanate oxides with the same stoichiometry can be understood in terms of differences in their structures and compositions. While the radiation damage susceptibility of pyrochlore A₂B₂O₇ materials decreases as a function of themore » cation radius ratio rA/rB, the current study correlates this behavior with the stability field of monoclinic structures, where rLa/rTi > rGd/rTi. Isochronal annealing experiments of the irradiated materials showed complete recrystallization of La₂Ti₂O₇ at 775 °C and of Gd₂Ti₂O₇ at 850 °C. The annealing behavior is discussed in terms of enhanced damage recovery in La₂Ti₂O₇, compared to the pyrochlore compounds Gd₂Ti₂O₇. As a result, the difference in the recrystallization behavior may be related to structural constraints, i.e., reconstructing a low symmetry versus a high symmetry phase.« less

Authors:

Park, Sulgiye ^[1]; Lang, Maik ^[2]; Tracy, Cameron L. ^[3]; Zhang, Jiaming ^[1]; Zhang, Fuxiang ^[3]; Trautmann, Christina ^[4]; Rodriguez, Matias D. ^[5]; Kluth, Patrick ^[5]; Ewing, Rodney C. ^[1]

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+ Show Author Affiliations

1. Stanford Univ., CA (United States)
2. Univ. of Tennessee, Knoxville, TN (United States)
3. Univ. of Michigan, Ann Arbor, MI (United States)
4. GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt (Germany); Technische Univ. Darmstadt (Germany)
5. Australian National Univ., Canberra (Australia)

Publication Date:

Mon Apr 27 00:00:00 EDT 2015

Research Org.:

Energy Frontier Research Centers (EFRC) (United States). Materials Science of Actinides (MSA)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1370869

Alternate Identifier(s):

OSTI ID: 1250995

Grant/Contract Number:  

SC0001089; DMR-0225180; DMR-987177; DMR-0723032

Resource Type:

Accepted Manuscript

Journal Name:

Acta Materialia

Additional Journal Information:

Journal Volume: 93; Journal Issue: C; Related Information: MSA partners with University of Notre Dame (lead); University of California, Davis; Florida State University; George Washington University; University of Michigan; University of Minnesota; Oak Ridge National Laboratory; Oregon state University; Rensselaer Polytechnic Institute; Savannah River National Laboratory; Journal ID: ISSN 1359-6454

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; nuclear (including radiation effects); materials and chemistry by design; synthesis (novel materials); synthesis (self-assembly); pyrochlores; perovskites; swift heavy ion; annealing; X-ray diffraction