Abstract:
Three Bismuth based superconducting samples with the composition.rPbQ.sSrCaCui.sOy were prepared using different solid state reaction techniques. The BiiOz* P6O, SrCOz and CuO powders o/99% purity were used as starting raw materials. The powders were mixed with the nominal cation ratio Bi : Pb : Sr : Ca : Cu = 0.7 : 0.3 : 1 : 1 : 1.5 and then mixed well using dry grinding, wet grinding and wet ball milling methods. The powders were calcined at 820°C and pallets of diameter
13 mm and thickness 1 — 2 mm were prepared from the calcined powder under 300 kg cm~2 pressure. The samples were then sintered at different appropriate temperatures.
The resistance measurements at low temperatures were performed on three samples using a resistivity probe in the temperature range from 55K to 200 JFf. The samples prepared by dry grinding, wet grinding and wet ball milling methods have shown the superconducting transition Temperatures TC at 112K, 115X and IWK respectively. TCO of the three samples were found to be 7QK,8QK and 6&K respectively. In this work we developed a technique and successfully achieved a temperature as
low as 55K while the resistivity probe was in liquid nitrogen.
