Energetic Ion Irradiation-Induced Disordered Nanochannels for Fast Ion Conduction
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Atomically disordered oxides are seen as suitable candidate for fast oxygen conduction due to their remarkable enhancement in oxygen diffusivity compared with ordered oxides. In particular, disordered derivatives of pyrochlore-structured oxides (A2B2O7) are seen as an interesting prospect due to the intrinsic existence of oxygen vacancies in their lattice. Using energetic ion irradiation, we demonstrated fabrication of structurally disordered nanoscale channels in A2B2O7 (A = Gd, Yb; B = Ti, Zr) that act as selective pathways for fast oxygen conduction. Atomic-level characterization revealed that the amorphous core and surrounding defect-fluorite phase in the nanochannels exhibited distorted and differently coordinated Ti-O polyhedra, with very similar electronic structure. The formation of defect-fluorite structure is facilitated by a decrease in the difference between the ionic radii of A- and B-site cations in the lattice.
R.S. acknowledges the National Academy of Sciences (NAS), USA, for the award of an NRC research fellowship. This research was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division under Contract No. DE-AC05-00OR22725. We acknowledge that the 55-MeV I ion irradiation was performed at the Ion Beam Center of Helmholtz-Zentrum Dresden-Rossendorf.
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