Potassium substitution in the Bi2Sr2CaCu2Oy superconductor

Samples with the nominal composition Bi2Sr2-xKxCaCu2Ox (with x = 0.1, 0.2, 0.3, 0.4 and 0.5) were prepared by the solid state reaction method. The role of potassium at the Sr-site and the effect of various heat treatments in the 2212 composition were studied. From the X-ray diffraction data it is found that the samples annealed for longer have shown a single phase 2212 up to x = 0.4 dopant level. From d.c. four probe electrical resistance data, it was found that the Tc(0) varies from 76 to 93 K for different dopant levels. The diamagnetic nature of the samples was confirmed by a.c. susceptibility measurements. The phase formation of 2212 and the presence of potassium in the doped samples was confirmed by electron microprobe analysis.