POTASSIUM SUBSTITUTION IN THE BI2SR2CACU2OY SUPERCONDUCTOR

Samples with the nominal composition Bi2Sr2-xKxCaCu2Oy (with x = 0.1, 0.2, 0.3, 0.4 and 0.5) were prepared by the solid state reaction metho d. 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 diffr action data it is found that the samples annealed for longer have show n a single phase 2212 up to x = 0.4 dopant level. From d.c. four probe electrical resistance data, it was found that the T(c)(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 w as confirmed by electron microprobe analysis.