The Effect of Long Annealing on Pb-Doped High-Tc BiSrCaCuO Systems

Abstract

The lead doped Bi based copper oxide high-T, superconductors with different nominal compositions and with different annealing time periods are studied. The highest T, (zero) achieved is 112 K in bulk phase 2223. The varying intensity of the low angle line at 28 z 4.7" suggests the gradual formation of the high-TT, phase due to the long annealing of nearly 200 to 250 h. It is also found that the high-T, phase starts degrading after 250 h of annealing and T, reduces. The distortion of thc 2223 phase is suggested by the broadening of different XRD peaks, also the SEM studies support the above contention. The EDAX studies show no presence of Pb in the crystallites. Es werden Blei-dotierte Bi-Kupferoxyd-Hoch-T,-Supraleiter mit variabler Zusammensetzungen untersucht, die wahrend unterschiedlicher Zeiten getempert wurden. Das hochste T, von 112 K wird bei der 2223-Volumenphase beobachtet. Die Intensitatsvariation der Kleinwinkellinie bei 20 z 4;7" laBt auf eine allmahliche Bildung der Hoch-T,-Phase wahrend der langen Temperzeit von ca. 200 bis 250 h schlieBen. Ferner ist gefunden worden, daB die Hoch-T.-Phase nach einer Temperzeit von 250 h degradiert und daB T. abnimmt. Die Degradation der 2223-Phase wird aus der Verbreiterung verschiedener Beugungsmaxima geschlossen, diese SchluBfolgerung wird durch REM-Untersuchungen gestiitzt. Die EDAX-Untersuchungen zeigen, daB in den Kristalliten kein Pb vorhanden ist.

The Effect of Sb Substitution of Cu in Bi1.7Pb0.3Sr2Ca2Cu3—xSbxOy Superconductors

“…4. Platelike grains about 5 to 10 mm in size seem to dominate these structures which are probably responsible for superconductivity [17,19]. The platelike grain size seems to be smallest in sample C and largest in sample D. Along with these platelike grains a second finer phase can be easily identified in these micrographs.…”

The Effect of Sb Substitution of Cu in Bi1.7Pb0.3Sr2Ca2Cu3?xSbxOy Superconductors

“…4. Platelike grains about 5 to 10 mm in size seem to dominate these structures which are probably responsible for superconductivity [17,19]. The platelike grain size seems to be smallest in sample C and largest in sample D. Along with these platelike grains a second finer phase can be easily identified in these micrographs.…”