VARIATION OF Tc IN SINGLE PHASE Bi4Sr3Ca3Cu4O16−x SYSTEM
The variation of critical temperature Tc in a single-phased ceramic high temperature superconductor Bi 4 Sr 3 Ca 3 Cu 4 O y is studied using techniques like X-ray diffraction, magnetic and electrical measurements. Samples of Bi-Sr-Ca-CuO having nominal composition 4334 are synthesized by solid state reaction using appropriate amounts of Bi 2O3, SrCO 3, CaCO 3 and CuO powders. It has been shown that the Tc in this material can be raised from 98 K in the fast quenched sample to 120 K in the furnace-cooled one. The higher values of Tc in furnace cooled specimens as compared with the Tc in quenched samples have been attributed to the variation in the interlayer spacing in these compounds. It is concluded that electron density and hence the attractive interaction between pairs are increased due to shortening of the interlayer spacing in the furnace-cooled sample, leading to an increase of its Tc.