100-K superconducting phases in the Tl-Ca-Ba-Cu-O system

Abstract

Two superconducting phases, ${\mathrm{Tl}}_{2}$${\mathrm{Ca}}_{2}$${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{10+\mathrm{\ensuremath{\delta}}}$ (2223) and ${\mathrm{Tl}}_{2}$${\mathrm{Ca}}_{1}$${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{2}$${)}_{8+\mathrm{\ensuremath{\delta}}}$ (2122), both with onset ${\mathrm{T}}_{\mathrm{c}}$ near 120 K and zero resistivity at 100 K, have been isolated from samples in the Tl-Ca-Ba-Cu-O system. The new 2223 superconductor has a 5.40\ifmmode\times\else\texttimes\fi{}5.40\ifmmode\times\else\texttimes\fi{}36.25-A${\mathrm{\r{}}}^{3}$ pseudotetragonal unit cell. The 2122 superconductor, which appears to be structurally related to ${\mathrm{Bi}}_{2}$${\mathrm{CaSr}}_{2}$${\mathrm{Cu}}_{2}$${\mathrm{O}}_{8+\mathrm{\ensuremath{\delta}}}$, has a 5.44\ifmmode\times\else\texttimes\fi{}5.44\ifmmode\times\else\texttimes\fi{}29.55-A${\mathrm{\r{}}}^{3}$ pseudotetragonal subcell. The 2223 phase is probably related to 2122 by the addition of extra calcium and copper layers.