Role of lead in the growth of the high T<inf> c</inf> phase in the Bi<inf>2-x</inf> Pb<inf> x</inf> Sr<inf>2</inf>Ca<inf>2</inf>Cu<inf>3</inf>O<inf> y</inf> systems

Bi2-x Pb x Sr2Ca2Cu3O y superconducting samples with 0<x<0·3 have been synthesized and characterized using X-ray powder diffraction. T c and superconducting volume fraction have been measured using a.c. magnetic susceptibility, d.c. electrical resistivity as well as X-band microwave surface resistance in the normal state. The data indicate the growth of the high T c (2223) phase with corresponding reduction of the low T c (2122) phase with increasing x, up to 0·25. Beyond this value of x there is a slight deterioration of the superconducting behaviour. © 1991 Indian Academy of Sciences.