Microstructural and magnetic studies of sinter-forged (Bi, Pb)₂Sr₂Ca₂Cu₃O_x superconductor

The microstructural and magnetic properties of sinter-forged BiPbSrCaCuO superconductors have been studied. The as-sinter-forged sample consisted of significant microcracks all through the bulk and first forms into a Bi 2-2-1-2 phase (c = 3.08 nm). However, after heat treatment at 860°C in air for 10 days, the final sample transformed to microstructurally smooth grains of Bi 2-2-2-3 phase (c = 3.70 nm). ac magnetic susceptibility data taken at 0.1, 1 and 10 Oe evidence the onset of diamagnetic response of grains at T_c = 105 K with a rather narrow transition width, ΔT_c = 3 K. TEM, SEM and XRD analyses reveal remarkable microstructural changes into a smooth laminar structure during the formation of Bi 2-2-2-3 phase.