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Enhanced current transport at grain boundaries in high-Tc superconductors

Nature volume 435, pages 475–478 (2005)Cite this article

Abstract

Large-scale applications of high-transition-temperature (high-Tc) superconductors, such as their use in superconducting cables, are impeded by the fact that polycrystalline materials (the only practical option) support significantly lower current densities than single crystals1,2,3,4,5,6. The superconducting critical current density (Jc) across a grain boundary drops exponentially if the misorientation angle exceeds 2°–7°. Grain texturing reduces the average misorientation angle, but problems persist7,8. Adding impurities (such as Ca in YBa2Cu3O7-δ; YBCO) leads to increased Jc (refs 9, 10), which is generally attributed to excess holes introduced by Ca2+ substituting for Y3+ (ref. 11). However, a comprehensive physical model for the role of grain boundaries and Ca doping has remained elusive. Here we report calculations, imaging and spectroscopy at the atomic scale that demonstrate that in poly-crystalline YBCO, highly strained grain-boundary regions contain excess O vacancies, which reduce the local hole concentration. The Ca impurities indeed substitute for Y, but in grain-boundary regions under compression and tension they also replace Ba and Cu, relieving strain and suppressing O-vacancy formation. Our results demonstrate that the ionic radii are more important than their electronic valences for enhancing Jc.

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Figure 1: First-principles calculations of Ca and O vacancy formation energy in bulk YBCO.
Figure 2: Structural differences in pristine and Ca-doped YBCO.

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References

  1. Dimos, D., Chaudhari, P. & Mannhart, J. Superconducting transport properties of grain boundaries in YBa2Cu3O7 bicrystals. Phys. Rev. B 41, 4038–4049 (1990)

    Article  ADS  CAS  Google Scholar 

  2. Gross, R. & Mayer, B. Transport processes and noise in YBa2Cu3O7-δ grain-boundary junctions. Physica C 180, 235–242 (1991)

    Article  ADS  CAS  Google Scholar 

  3. Gurevich, A. & Pashitskii, E. A. Current transport through low-angle grain boundaries in high-temperature superconductors. Phys. Rev. B 57, 13878–13893 (1998)

    Article  ADS  CAS  Google Scholar 

  4. Heinig, N. F. et al. Evidence for channel conduction in low misorientation angle [001] tilt YBa2Cu3O7-x bicrystal films. Appl. Phys. Lett. 69, 577–579 (1996)

    Article  ADS  CAS  Google Scholar 

  5. Hilgenkamp, H. & Mannhart, J. Grain boundaries in high-Tc superconductors. Rev. Mod. Phys. 74, 485–549 (2002)

    Article  ADS  CAS  Google Scholar 

  6. Mannhart, J., Chaudhari, P., Dimos, D., Tsuei, C. C. & McGuire, T. R. Critical currents in [001] grains and across their tilt boundaries in YBa2Cu3O7 films. Phys. Rev. Lett. 61, 2476–2479 (1988)

    Article  ADS  CAS  Google Scholar 

  7. Iijima, Y. et al. Structural and transport-properties of biaxially aligned YBa2Cu3O7-x films on polycrystalline Ni-based alloy with ion-beam-modified buffer layers. J. Appl. Phys. 74, 1905–1911 (1993)

    Article  ADS  CAS  Google Scholar 

  8. Norton, D. P. et al. Epitaxial YBa2Cu3O7 on biaxially textured nickel (001): An approach to superconducting tapes with high critical current density. Science 274, 755–757 (1996)

    Article  ADS  CAS  Google Scholar 

  9. Hammerl, G. et al. Enhanced supercurrent density in polycrystalline YBa2Cu3O7-δ at 77 K from calcium doping of grain boundaries. Nature 407, 162–164 (2000)

    Article  ADS  CAS  Google Scholar 

  10. Schmehl, A. et al. Doping-induced enhancement of the critical currents of grain boundaries in YBa2Cu3O7-δ . Europhys. Lett. 47, 110–115 (1999)

    Article  ADS  CAS  Google Scholar 

  11. Kucera, J. T. & Bravman, J. C. Transport characterization of calcium-doped YBa2Cu3O7-δ thin films. Phys. Rev. B 51, 8582–8590 (1995)

    Article  ADS  CAS  Google Scholar 

  12. Daniels, G. A., Gurevich, A. & Larbalestier, D. C. Improved strong magnetic field performance of low angle grain boundaries of calcium and oxygen overdoped YBa2Cu3Ox . Appl. Phys. Lett. 77, 3251–3253 (2000)

    Article  ADS  CAS  Google Scholar 

  13. Guth, K., Krebs, H. U., Freyhardt, H. C. & Jooss, C. Modification of transport properties in low-angle grain boundaries via calcium doping of YBa2Cu3O7-δ thin films. Phys. Rev. B 64, 140508 (2001)

    Article  ADS  Google Scholar 

  14. Schofield, M. A., Beleggia, M., Zhu, Y. M., Guth, K. & Jooss, C. Direct evidence for negative grain boundary potential in Ca-doped and undoped YBa2Cu3O7-x . Phys. Rev. Lett. 92, 195502 (2004)

    Article  ADS  Google Scholar 

  15. Kung, H. et al. Dissociation of grain boundary dislocations in YBa2Cu3O7-δ-coated conductors. Phil. Mag. Lett. 81, 85–93 (2001)

    Article  ADS  CAS  Google Scholar 

  16. Song, X., Daniels, G. A., Feldmann, D. M., Gurevich, A. & Larbalestier, D. C. Electromagnetic, atomic-structure and chemistry changes induced by Ca-doping of low angle YBCO grain boundaries. Nature Mater. (submitted)

  17. Kim, M. et al. Nonstoichiometry and the electrical activity of grain boundaries in SrTiO3 . Phys. Rev. Lett. 86, 4056–4059 (2001)

    Article  ADS  CAS  Google Scholar 

  18. Klie, R. F., Beleggia, M., Zhu, Y., Buban, J. P. & Browning, N. D. Atomic-scale model of the grain boundary potential in perovskite oxides. Phys. Rev. B 68, 214101 (2003)

    Article  ADS  Google Scholar 

  19. Su, H. B. & Welch, D. O. Effects of space charge, dopants, and strain fields on surfaces and grain boundaries in YBCO compounds. Supercond. Sci. Technol. 18, 24–34 (2005)

    Article  ADS  CAS  Google Scholar 

  20. Browning, N. D. et al. The atomic origins of reduced critical currents at [001] tilt grain boundaries in YBa2Cu3O7-δ thin films. Physica C 294, 183–193 (1998)

    Article  ADS  CAS  Google Scholar 

  21. Zhu, Y., Zuo, J. M., Moodenbaugh, A. R. & Suenaga, M. Grain boundary constraint and oxygen deficiency in YBa2Cu3O7-δ. Phil. Mag. A 70, 969–984 (1994)

    Article  ADS  CAS  Google Scholar 

  22. Allen, L. J., Findlay, S. D., Lupini, A. R., Oxley, M. P. & Pennycook, S. J. Atomic-resolution electron energy loss spectroscopy imaging in aberration corrected scanning transmission electron microscopy. Phys. Rev. Lett. 91, 105503 (2003)

    Article  ADS  CAS  Google Scholar 

  23. Browning, N. D., Chisholm, M. F. & Pennycook, S. J. Atomic-resolution chemical analysis using a scanning transmission electron microscope. Nature 366, 143–146 (1993)

    Article  ADS  CAS  Google Scholar 

  24. Varela, M. et al. Spectroscopic imaging of single atoms within a bulk solid. Phys. Rev. Lett. 92, 095502 (2004)

    Article  ADS  CAS  Google Scholar 

  25. Cherns, D. & Jiao, C. G. Electron holography studies of the charge on dislocations in GaN. Phys. Rev. Lett. 87, 205504 (2001)

    Article  ADS  CAS  Google Scholar 

  26. Nellist, P. D. et al. Direct sub-angstrom imaging of a crystal lattice. Science 305, 1741 (2004)

    Article  CAS  Google Scholar 

  27. Egerton, R. F. Electron Energy Loss Spectroscopy in the Electron Microscope (Plenum, New York, 1986)

    Google Scholar 

  28. Kresse, G. & Furthmuller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169–11186 (1996)

    Article  ADS  CAS  Google Scholar 

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Acknowledgements

We thank D.W. Gillette for the sample preparation and A.R. Lupini for his help in acquiring the images of Ca-doped YBCO. This work is supported by the US Department of Energy, Division of Materials Sciences, Office of Basic Energy Science and the National Energy Research Scientific Computing Center, supported by the Office of Science of the US Department of Energy.

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Authors and Affiliations

  1. Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York, 11973, USA

    R. F. Klie & Y. Zhu

  2. Institute of Engineering Innovation, The University of Tokyo, Tokyo, 113-8656, Japan

    J. P. Buban

  3. Condensed Matter Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA

    M. Varela, A. Franceschetti, S. T. Pantelides & S. J. Pennycook

  4. Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee, 37235, USA

    A. Franceschetti, S. T. Pantelides & S. J. Pennycook

  5. Institut für Materialphysik, University of Göttingen, 37073, Göttingen, Germany

    C. Jooss

  6. Department of Chemical Engineering and Materials Science, University of California-Davis, Davis, California, 95616, USA

    N. D. Browning

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Correspondence to R. F. Klie.

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Supplementary information

Supplementary Figure S1

The relative pre-peak intensity of the oxygen K-edge as a function of position within the dislocation core for pristine and Ca-doped YBa2Cu3O7-δ. (DOC 97 kb)

Supplementary Figure S2

Two EELS spectra containing the Ca L-edge and the O K-edge for Ca-doped YBa2Cu3O7-δ taken from the centre of the grain boundary dislocation core and the bulk of the sample. (DOC 187 kb)

Supplementary Figure S3

Two EELS spectra containing the O K-edge and the Ba M-edge for pristine YBa2Cu3O7-δ taken from the centre of the grain boundary dislocation core and the bulk of the sample. (DOC 157 kb)

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Klie, R., Buban, J., Varela, M. et al. Enhanced current transport at grain boundaries in high-Tc superconductors. Nature 435, 475–478 (2005). https://doi.org/10.1038/nature03644

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