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Diffusion Mechanism of Cations and Anions in Cation-Exchange Process for Fabrication of High-Tc Superconducting HgBa2CaCu2O6+δ?Films

Published online by Cambridge University Press:  18 March 2011

Y. Y. Xie ,
J. Z. Wu ,
T. Aytug  and
D. K. Christen
Y. Y. Xie
Affiliation:
Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045 USA
J. Z. Wu
Affiliation:
Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045 USA
T. Aytug
Affiliation:
Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
D. K. Christen
Affiliation:
Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
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Abstract

We have investigated the diffusion mechanism of Hg and Tl cations in cation-exchange process that has been used successfully for fabrication of Hg-based high-Tc superconducting films. Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) was employed to map the distribution of Tl and Hg cations in films quenched at different stages of the cation exchange process. SEM/EDS mappings showed that the nonuniform distribution of Hg is visible in micrometer size on the surface of samples quenched after short-time (∼10min) Hg-annealing, but this nonuniformity disappears for longer-time (∼45 min) Hg-annealing samples. This change could be ascribed to different stages in Hg diffusion -- the former is the early stage when Hg is concentrated in the channels and the latter Hg-cations have already diffuse to grains. Our experimental results hence suggest that Hg-cations channel through defects in the films then diffuse into grains along a-b planes and vise versa for Tl-cations. The diffusion mechanism of anions (oxygen) in post annealing has also been discussed. Fluorine-doped Hg-1212 films were post annealed in flowing oxygen at 300 °C for several hours. Magnetic measurement has shown these samples are comprised pure overdoped Hg-1212 phase with smooth and sharp transition below 120 K, but resistivity vs. temperature measurement shows a kink at ∼123 K. This implies that the optimally doped Hg-1212 phase with higher Tc might be surrounded by overdoped Hg-1212 phase and their contribution to magnetization is minimized, thus the possible diffusion mechanism for anions is also through grain boundaries at a much larger time scale compared to the cations.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 689: Symposium E – Materials for High-Temperature Superconductor Technologies , 2001 , E4.4
Copyright
Copyright © Materials Research Society 2002

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References

REFERENCES

[1] Putilin, S. N., Antipov, E. V., Chmaissem, O., and Marezio, M., Nature 362, 226 (1993).Google Scholar
[2] Schilling, A., Cantoni, M., Guo, J. D., and Ott, H. R., Nature 363, 56 (1993).Google Scholar
[3] Krusin-Elbaum, L., Tsuei, C. C., and Gupta, A., Nature 373, 679 (1995).Google Scholar
[4] Wu, J.Z., Yan, S.L., Xie, Y.Y., App. Phys. Lett. 74, 1469 (1999).Google Scholar
[5] Xie, Y.Y., Wu, J.Z., Gapud, A.A., Yang, Y., Xin, Y., Physics C 322, 19 (1999).Google Scholar
[6] Yan, S. L., Xie, Y.Y., Wu, J. Z., Aytug, T., Gapud, A.A., Kang, B.W., Fang, L., He, M., Tidrow, S.C., Kirchner, K.W., Liu, J.R. and Chu, W.K., App. Phys. Lett. 73, 2989 (1998).Google Scholar
[7] Aga, R. Jr, Yan, S.L., Xie, Y.Y., Han, S., Wu, J.Z., Jia, Q.X., Kwon, C., App. Phys. Lett. 76, 1606 (2000).Google Scholar
[8] Aga, R. Jr., Xie, Y.Y., Yan, S.L., Wu, J.Z., Han, S., App. Phys. Lett. 79, 2417 (2001).Google Scholar
[9] Xie, Y.Y., Aytug, T., Wu, J.Z., Verebelyi, D.T., Paranthaman, M., Goyal, A., and Christen, D.K., App. Phys. Lett. 77, 4193 (2000).Google Scholar
[10] Xie, Y.Y., Wu, J.Z., Albert, A.H., unpublished.Google Scholar
[11] Lee, W.Y., Lee, V.Y., Salem, J., Huang, T.C., Savoy, R., Bullock, D.C., and Parkin, S.S.P., Appl. Phys. Lett. 53, 329 (1988).Google Scholar
[12] Siegal, M. P., Venturini, E. L., and Aselage, T. L., J. Mater. Res. 12, 2825 (1997).Google Scholar
[13] Wang, X.-G., Huang, Z., Yuan, L., Physica C, 253, 254 (1995).Google Scholar
[14] Xie, Y.Y., Wu, J.Z., “Critical current density enhancement in fluorine-assisted overdoped HgBa2CaCu2O6+δ?thin films”, preprint.Google Scholar