New TI-1223 bulk superconductors with high phase purity and Tcro, between 110 K and 118 K have been synthesized byvarying the ratios of Srto Ba and of TI to Pb and/or Bi in the (TLCmmmBimPbn) (Sr,d3a,)Ca2Cua0, . . . ~ . .superconducting system in the composition range m = ' 0 4 : 4 , n = 0 4 . 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 Tcco, value to about 79 K. Replacement of Pb or TI 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 ~lo.~sPbo.4)(Sr,.~Bao.4)Ca2Cu30, and (T10.63Bi0.1 Pbo.n)(Srr.sBao.4)Ca2Cu30,. 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 c m 2 and 1200 A cm-2 respectively, and the TCm, values 11 1 K with transition widths of 1 K.

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