Composition dependence of high T c phase formation in Pb-doped Bi-Sr-Ca-Cu-O thin films

Abstract

We studied the composition dependence of high Tc phase Bi2Sr2Ca2Cu3Ox formation in Pb-doped Bi system thin films. Films were prepared by rf magnetron sputtering using three targets and post-annealed to synthesize superconducting films. In addition to a Bi-Sr-Ca-Cu-O target, PbO and CuO targets were used to dope sufficient Pb into the films and to optimize the Cu content. Although heavily Pb-doped thin films form the high Tc phase rapidly, they are multiphased and have poor morphology. The Cu content decreases slightly during sintering. Minimizing the amount of doped Pb needed for the high Tc phase formation improves morphology, and slightly Cu-rich composition is effective in forming the high Tc phase. Nearly single-phase high Tc films were obtained from the as-deposited compositions of Bi:Pb:Sr:Ca:Cu=1.02:0.80:1.00:0.99:1.64 after only one hour of sintering in air at 851 °C. The single-phase high Tc film forms in a very narrow sintering temperature range.