Ceramics-Silikáty 49, (1) 23 - 28 (2005) |
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EFFECTS OF POST-OXYGEN ANNEALING AND LANTHANUM DOPING ON INTER- AND INTRA-GRAIN PROPERTIES OF (Tl,Pb)-1223 SUPERCONDUCTORS
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Cigáň Alexander 1, Plesch Gustav 2, Maňka Ján 1,
Hanic František 1,
Kopčok Michal 1,
Koňakovský Anton 1,
Kliment Juraj 2,
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1 Institute of Measurement Science, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia
2 Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University, 842 15 Bratislava, Slovakia
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Keywords: (Tl,Pb)-1223 based superconductors, La³⁺ doping, Magnetization, SQUID gradiometer, Ageing
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Effects of oxygen annealing and low level La³⁺ doping of the (Tl,Pb)-1223 system have been investigated. Samples with the
nominal composition (Tl0.6Pb0.5)(Sr0.8Ba0.2)2Ca2₂Cu₃O8+δ - x LaO1.5, where x ranges from 0.00 to 0.10, were synthesized using a
sol-gel process. Their superconducting inter- and intra-grain properties, phase compositions, and microstructure were studied.
XRD results prove that (Tl,Pb)-1223 is the dominant phase in all samples. The La doping initiates a formation of the
(Tl,Pb)-1212 phase and decreases the volume superconducting properties. The post oxygen annealing strongly improves intergrain
superconducting links and leads to a positive effect on the critical temperature, Tcon. and the ∆Tcon. The central peak of
magnetization hysteresis loops around zero field is found to be in an anomalous positive position on the descending branch
of the external field. |
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