Seeing oxygen disorder in YSZ/SrTiO_(3) colossal ionic conductor heterostructures using EELS



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Pennycook, T. J. and Oxley, M. P. and Garcia Barriocanal, Javier and Bruno, F. Y. and León Yebra, Carlos and Santamaría Sánchez-Barriga, Jacobo and Pantelides, S. T. and Varela del Arco, María and Pennycook, S. J. (2011) Seeing oxygen disorder in YSZ/SrTiO_(3) colossal ionic conductor heterostructures using EELS. European physical journal-applied physics, 54 (3). ISSN 1286-0042

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Colossal ionic conductivity was recently discovered in YSZ/SrTiO_(3) multilayers and was explained in terms of strain- and interface-enhanced disorder of the O sublattice. In the present paper we use a combination of scanning transmission electron microscopy and electron energy loss spectroscopy (EELS) and theoretical EELS simulations to confirm the presence of a disordered YSZ O sublattice in coherent YSZ/SrTiO_(3) multilayers. O K-edge fine structure simulated for the strained disordered O sublattice phase of YSZ possesses blurred-out features compared to that of ordered cubic bulk YSZ, and experimental EELS fine structure taken from the strained YSZ of coherent YSZ/SrTiO_(3) thin films is similarly blurred out. Elemental mapping is shown to be capable of resolving ordered YSZ O sublattices. Elemental mapping of O in the coherent YSZ/STO multilayers is presented in which the O sublattice is seen to be clearly resolved in the STO but blurred out in the YSZ, indicating it to be disordered. In addition, we present imaging and EELS results which show that strained regions exist at the incoherent interfaces of YSZ islands in STO with blurred out fine structure, suggesting these incoherent regions may also support high ionic conductivities. Recently, Cavallaro et al. reported electronic conductivities in samples of incoherent disconnected islands embedded in STO that are similar to the islands described herein. The presence of a region of O depleted STO at the interface with incoherent YSZ islands is revealed by EELS elemental mapping, implying the n-type doping of STO/YSZ nanocomposites with disconnected incoherent YSZ islands.

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© EDP Sciences. The authors are grateful to C. Cantoni for the bulk YSZ sample, M. Watanabe for the PCA plug in for Digital Micrograph and J. Luck for sample preparation. Research at Oak Ridge National Laboratory was sponsored by the US Department of Energy, Office of Science, Materials Sciences and Engineering Division (MPO, MV, SJP). Research at Vanderbilt was supported in part by the US Department of Energy Grant DEFG02- 09ER46554 (TJP, STP) and the McMinn Endowment (STP). Research at Universidad Complutense was supported by the Spanish Ministry for Science and Innovation, and the Madrid Regional Government. Computations were performed at the National Energy Research Scientific Computing Center at Lawrence Berkeley National Laboratory.

Uncontrolled Keywords:Epitaxial ZrO_(2)Y_(2)O_(3)/SrTiO_(3) heterostructures; Activation-energy; Grain-boundaries; YSZ; Interafaces; Transport; Superlattices; Multilayers; Ionization; Crystals.
Subjects:Sciences > Physics > Electricity
Sciences > Physics > Electronics
ID Code:30258
Deposited On:22 May 2015 09:47
Last Modified:10 Dec 2018 14:58

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