Fabrication, phase composition and properties of (Tl, Bi, Pb)(Sr, Ba)<sub>2</sub>Ca<sub>2</sub>Cu<sub>3</sub>O<sub>z</sub> superconductors
M Mair; W T Konig; G Gritzner; M Mair; Inst. fur Chem. Technol. Anorganischer Stoffe, Johannes Kepler Univ., Linz, Austria; W T Konig; Inst. fur Chem. Technol. Anorganischer Stoffe, Johannes Kepler Univ., Linz, Austria; G Gritzner; Inst. fur Chem. Technol. Anorganischer Stoffe, Johannes Kepler Univ., Linz, Austria
Журнал:
Superconductor Science and Technology
Дата:
1995-12-01
Аннотация:
New Ti-1223 bulk superconductors with high phase purity and T<sub>c(0)</sub> between 110 K and 118 K have been synthesized by varying the ratios of Sr to Ba and of Tl to Pb and/or Bi in the (Tl<sub>1-(m+n)</sub>Bi<sub>m</sub>Pb<sub>n</sub>) (Sr<sub>2-y</sub>Ba<sub>y</sub>)Ca<sub>2</sub>Cu<sub>3</sub>O<sub>z</sub> superconducting system in the composition range m=0-0.4, n=0-0.4 and y=0.2 or 0.4. A decrease in the Ba content to y=0.2 favoured the formation of the 1212 phase accompanied by a drop of the T<sub>c(0)</sub> value to about 79 K. Replacement of Pb or Tl by Bi above m=0.1 led to higher contents of the barium-bismuth oxide and calcium-strontium-copper oxide secondary phases. Best results were obtained for specimens with nominal overall compositions of (Tl<sub>0.55</sub>Pb<sub>0.4</sub>)(Sr<sub>1.6</sub>Ba<sub>0.4</sub>)Ca<sub>2</sub>Cu<sub>3</sub>O<sub>z</sub> and (Tl<sub>0.63</sub>Bi<sub>0.1</sub>Pb<sub>0.2</sub>)(Sr<sub>1.6</sub>Ba<sub>0.4</sub>)Ca<sub>2</sub>Cu<sub>3</sub>O<sub>z</sub>. The X-ray diffraction spectra for these compositions could almost exclusively be assigned to the 1223 phase. The critical current densities at 77 K were 1600 A cm<sup>-2</sup> and 1200 A cm<sup>-2</sup> respectively, and the T<sub>c(0)</sub> values 111 K with transition widths of 1 K.
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