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Oxygen Deficient YBa 2 Cu 3 O 7-δ : Two Superconducting Phases |
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J. Stankowski
a
, A. Ślązak
a
, W. Kempiński
a
, B. Andrzejewski
a
, B. Reichel
b
and G. Plesch
c
a Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznań, Poland b Faculty of Applied Physics and Mathematics, Technical University of Gdańsk, Narutowicza 11/12, 80-952 Gdańsk, Poland c Department of Inorganic Chemistry, Faculty of Natural Sciences Comenius University, 842 15 Bratislava, Slovakia |
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| Received: October 6, 2003; revised version December 19, 2003 |
| A set of oxygen deficient powder and granular samples of YBa 2 Cu 3 O 7-δ ceramics was studied by means of thermogravimetric and magnetically modulated microwave absorption methods. Especially the last method has turned out to be a powerful method, which was used to determine the dependence of critical temperature T c on the oxygen parameter δ. Using these methods it has been shown that the removing of oxygen evokes the inhomogeneous oxygen distribution in the samples and a change in carrier concentration till to the loss of superconducting properties. A superconducting phase with $T\rm_c=60$~K, which occurs in oxygen deficient YBa 2 Cu 3 O 7-δ sample, is an unstable phase. |
| PACS numbers: 74.72.--h, 74.62.Bf, 74.62.--c, 74.25.Nf |