Pb-doped Tl-Ba-Ca-Cu-O compounds with nominal composition ${\mathrm{TlPb}}_{\mathrm{x}}$${\mathrm{BaCa}}_3$${\mathrm{Cu}}_3$${\mathrm{O}}_{\mathrm{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 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 $T_c$ for the Pb-doped samples has also been studied. It is found that $T_c$ increases with pressure at a rate of ${\mathrm{dT}}_c^{R=0\mathrm{}}$/dP=0.22 K/kbar for x=0.5, a higher rate than the ${\mathrm{dT}}_c^{R=0\mathrm{}}$/dP=0.18 K/kbar for pure Tl-Ba-Ca-Cu-O.

• Received 2 August 1989

DOI:https://doi.org/10.1103/PhysRevB.41.2517