Amorphization of Ta2O5 under swift heavy ion irradiation

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS

卷:407

Article

Cusick, Alex B.¹  Lang, Maik²  Zhang, Fuxiang³  Sun, Kai¹  Li, Weixing⁴  Kluth, Patrick⁵  Trautmann, Christina^6,7  Ewing, Rodney C.^1,3,4 

[1] Univ Michigan, Mat Sci & Engn, Ann Arbor, MI 48109 USA

[2] Univ Tennessee, Nucl Engn, Knoxville, TN 37996 USA

[3] Univ Michigan, Earth & Environm Sci, Ann Arbor, MI 48109 USA

[4] Stanford Univ, Geol Sci, Stanford, CA 94305 USA

[5] Australian Natl Univ, Res Sch Phys & Engn, Canberra, ACT 2601, Australia

[6] GSI Helmholtz Ctr Heavy Ion Res, D-64291 Darmstadt, Germany

[7] Tech Univ Darmstadt, D-64287 Darmstadt, Germany

关键词: Swift heavy ions;    Irradiation;    Phase transformation;    Tantalum oxide;    Amorphization;   

DOI  :  10.1016/j.nimb.2017.05.036

来源: Elsevier

【 摘 要 】

Crystalline Ta2O5 powder is shown to amorphize under 2.2 GeV Au-197 ion irradiation. Synchrotron X-ray diffraction (XRD), Raman spectroscopy, small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM) were used to characterize the structural transition from crystalline to fully amorphous. Based on Rietveld refinement of XRD data, the initial structure is orthorhombic (P2mm) with a very large unit cell (a = 6.20, b = 40.29, c = 3.89 angstrom; V = 971.7 angstrom(3)), ideally containing 22 Ta and 55 O atoms. At a fluence of approximately 3 x 10(11) ions/cm(2), a diffuse amorphous background becomes evident, increasing in intensity relative to diffraction maxima until full amorphization is achieved at approximately 3 x 10(12) ions/cm(2). An anisotropic distortion of the orthorhombic structure occurred during the amorphization process, with an approximately constant unitcell volume. The amorphous phase fraction as a function of fluence was determined, yielding a trend that is consistent with a direct-impact model for amorphization. SAXS and TEM data indicate that ion tracks exhibit a core-shell morphology. Raman data show that the amorphous phase is comprised of TaO6 and TaO5 coordination-polyhedra, in contrast to the TaO6 and TaO7 units that exist in crystalline Ta2O5. Analysis of Raman data shows that oxygen-deficiency increases with fluence, indicating a loss of oxygen that leads to an estimated final stoichiometry of Ta2O4,2 at a fluence of 1 x 10(13) ions/cm(2). (C) 2017 Elsevier B.V. All rights reserved.

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