Münster 1999 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 9: Postersitzung I: TT-Teilchendetektoren (1-7), TT-Techniken (8-11), 2-D-Systeme (12-21), Meso- u. nanoskopische Strukturen (22-44), Niederdim. Spinsysteme (45-60), Tunneln u. Symmetrien (61-65), SQUID-Anwendungen (66-73), Massive HTSL, Bandleiter (74-96)
TT 9.83: Poster
Dienstag, 23. März 1999, 09:30–12:30, Z
Influence of La doping on the growth and superconducting transition of BSCCO 2212 crystals and whiskers — •H. Jin*, A. Schley, and J. Kötzler — Institut für Angewandte Physik und Zentrum für Mikrostrukturforschung, Universität Hamburg
In the Bi2.4Sr2−xLaxCaCu2Oy (x=0-0.3) system
the influence of La doping
on the growth and superconducting transition has been studied. Single
crystals and whiskers were grown simultaneously from the melt in the
same crucible. This is a new way [1] to obtain superconducting whiskers,
since up to date 2212 whiskers were grown by annealing the melt-quenched
(Bi,Pb)SrCaCuO glasses in oxygen atmosphere. X-ray diffraction method was
used to determine the phases and to demonstrate the influence of La doping
on the c-axis lattice parameter. The superconducting onset temperature To
was determined by measurements of the magnetic ac-susceptibility.
The results show that all the La-doped crystals and whiskers are
of the 2212 single phase and the c-axis parameter decreases with the
doping level of La in the starting melt. La doping makes the To smaller
and the transition widths much broader for both the crystals and whiskers.
At the maximum doping (x=0.3), To is reduced to 62 K for the crystal,
but complete screening is not attained, while the whisker does not even
indicate any onset down to the lowest measured temperature of 10 K.
First data on oxygen annealed crystals and whiskers indicate a reduction
of the transition width but also a decrease of To. This effect is similar
to other reports on the BSCCO system where oxygen annealing improves the
homogeniety of the sample but lowers the transition temperature.
* Support by the Alexander von Humboldt Foundation
[1] Ichiro Matsubara et al, Appl. Phys. Lett. 56, 2141 (1990)