Superconductivity and its pressure dependence in the Pb-doped Tl-Ba-Ca-Cu-O superconductors

Pb-doped Tl-Ba-Ca-Cu-O compounds with nominal composition TlPb{sub {ital x}}BaCa{sub 3}Cu{sub 3}O{sub {ital y}} have been sintered, and their physical properties have been studied. It is found that the superconducting transition temperature of the samples drops with the increase of {ital x}. The crystal structure is tetragonal, and the lattice constants reduce with Pb content. Precipitated phases are also present in the Pb-doped samples. The pressure dependence of {ital T}{sub {ital c}} for the Pb-doped samples has also been studied. It is found that {ital T}{sub {ital c}} increases with pressure at a rate of {ital dT}{sub {ital c}}{sup {ital R}=0}/dP=0.22 K/kbar for {ital x}=0.5, a higher rate than the {ital dT}{sub {ital c}}{sup {ital R}=0}/dP=0.18 K/kbar for pure Tl-Ba-Ca-Cu-O.